Polymer particles, method of producing the same, and toner for use in electrophotography comprising the polymer particles

ABSTRACT

Polymer particles which are substantially spherical and have protrusions on the surface thereof, with such a particle size distribution that the volume mean diameter dv thereof is 1≦dv≦15 (μm), and the ratio of the volume mean diameter dv to the number mean diameter dn thereof, that is, dv/dn, is 1≦dv/dn≦1.2, are prepared, and used as a component for a toner for use in electrophotography.

This application is a division of application Ser. No. 08/449,424, filedMay 24, 1995, now U.S. Pat. No. 5,541,031 which is a continuation ofapplication Ser. NO. 165,101, filed Dec. 10, 1993, now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to polymer particles with a narrowparticle size distribution, which can be employed as spacers for use inelectronic appliances, a filler for use in a high functional separationcolumn, a molding material, a coating material, and microspheres havingactive surfaces for use in antigen-antibody reactions, and to a methodof producing the polymer particles, and also to a toner for use inelectrophotography comprising the polymer particles.

2. Discussion of Background

As the inventors of the present invention have disclosed in JapaneseLaid-Open Patent Application 61-19602, polymer particles with a narrowparticle size distribution in the range of 1 to 20 μm can be obtainedunder particular conditions by a polymerization method of polymerizing avinyl monomer in a hydrophilic organic liquid.

Based on this polymerization method, many trials have been made forchanging the composition and physical properties of the surface ofpolymer particles by using a different kind of polymer stabilizing agentor by providing chemical modifications to the surface of the polymerparticles.

However, polymer particles obtained by this polymerization method aresubstantially spherical and trials for changing the shape of the polymerparticles by using this polymerization method have not been made.

With respect to the field of toners for use in electrophotography, atoner comprising such spherical polymer particles with a small particlediameter and a narrow particle size distribution is suitable for highquality digital latent electrostatic images because the toner provideshigh quality images. However because the polymer particles employed inthe toner have a small particle size and are spherical, the cleaningperformance, image transfer performance and chargeability of the toner,in particular, the chargeability at high humidities, are so poor thatsuch a toner has not been employed in practice.

Japanese Laid-Open Patent Application 61-279864 discloses tonerparticles with the degree of the distortion from the complete sphericalshape of the toner particles being described in terms of the shapefactor thereof and with the degree of the unevenness of the surface ofthe toner particles being limited to a certain value. However, thereference does not mention anything about factors which have significanteffects on the characteristics of the toner, such as the particle sizedistribution of the toner and the composition of the protrusions on thesurface of the toner particles.

Japanese Laid-Open Patent Application 1-185653 discloses a tonercomprising toner particles which have a relatively narrow particle sizedistribution and are nearly spherical. However, the toner particlesthereof have very small protrusions or substantially crushed protrusionson the surface thereof, so that the height and composition of theprotrusions have not been taken into consideration when using the tonerparticles.

Furthermore, Japanese Laid-Open Patent Applications 1-300264 and2-187768 describe methods comprising the steps of preparing polymerparticles and attaching finely-divided particles to the surface of thepolymer particles in order to make the surface of the polymer particlesuneven. However, the methods described in the above references have theshortcomings that the finely-divided particles are not completelyattached to the surface of the polymer particles, so that some of thefinely-divided particles are detached from the surface of the polymerparticles, and the finely-divided particles are deformed. Furthermore,it is impossible to attach relatively large particles to the polymerparticles by the above methods in order to make the surface of thepolymer particles largely uneven.

SUMMARY OF THE INVENTION

It is therefore a first object of the present invention to providepolymer particles with a narrow particle size distribution, which havehigh fluidity and anti-blocking performance (i.e. non-aggregation ), andexcellent optical and dyeable characteristics.

A second object of the present invention is to provide a method ofproducing the above-mentioned polymer particles.

A third object of the present invention is to provide a toner comprisingthe above-mentioned polymer particles for use in electrophotography,which is capable of providing images with high quality, and hasexcellent cleaning performance and image transfer performance, and hightriboelectric chargeability which is stable regardless of the ambientconditions thereunder.

The first object of the present invention is achieved by polymerparticles which are substantially spherical and have protrusions on thesurface of each polymer particle, with such a particle size distributionthat the volume mean diameter dv thereof is 1≦dv≦15 (μm), and the ratioof the volume mean diameter dv to the number mean diameter dn, that is,dv/dn, is 1≦dv/dn≦1.2.

The second object of the present invention is achieved by apolymerization method comprising the steps of polymerizing a vinylmonomer in the presence of a polymeric dispersing agent in a hydrophilicorganic liquid in which the vinyl monomer is soluble, but in which apolymer formed from the vinyl monomer swells or is substantiallyinsoluble, optionally in the presence of a cross-linking agent and achain transfer agent, thereby preparing first polymer particles; andcontinuing the polymerization with the addition thereto of a vinylmonomer which, when polymerized, provides a polymer with a glasstransition point higher than that of the first polymer particles, and ananionic monomer or a cationic monomer, thereby producing polymerparticles which are substantially spherical and have protrusions on thesurface of each polymer particle, with a narrow particle sizedistribution.

The third object of the present invention is achieved by a tonercomprising the above-mentioned polymer particles which are uniformlydyed to the inside thereof.

The third object of the present invention is also achieved by a tonerconsisting of or comprising polymer particles with protrusions on thesurface of each polymer particle, which are substantially spherical,with the ratio of the average height h of the protrusions from thesurface of the polymer particles to the average diameter D of thepolymer particles which do not include the protrusions, that is, h/D,being 1/50≦h/D≦ 1/2, and the ratio of the surface area of the polymerparticles occupied by the protrusions to the entire surface of thepolymer particles being 1/20 or more.

The third object of the present invention is also achieved by a tonerconsisting of or comprising the above-mentioned polymer particles withprotrusions on the surface of each polymer particle, in which theprotrusions contain a functional group, and the functional group forms asalt by the reaction with a cationic surfactant or an anionicsurfactant.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the invention and many of the attendantadvantages thereof will be readily obtained as the same becomes betterunderstood by reference to the following detailed description whenconsidered in connection with the accompanying drawing, wherein:

FIG. 1 is a microscopic photograph of a toner prepared in Example 7taken by a scanning electron microscope.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Polymer particles of the present invention can be obtained, forinstance, by the following method:

At least one vinyl monomer A is polymerized in the presence of apolymeric dispersing agent in a hydrophilic organic liquid or in amixture of a hydrophilic organic liquid and water, in which the vinylmonomer A is soluble, but in which a polymer formed from the vinylmonomer A swells or is substantially insoluble, whereby a polymer isprepared from the vinyl monomer A.

At least one vinyl monomer B, which, when polymerized, provides apolymer with a glass transition point higher than that of the polymerprepared from the vinyl monomer A, and an anionic monomer or a cationicmonomer are added to the above polymer and polymerized, whereby polymerparticles which are substantially spherical and have protrusions on thesurface of each polymer particle are produced. The protrusions formed onthe surface of the polymer particles comprise as the main component acopolymer of the vinyl monomer B and the cationic monomer or the anionicmonomer.

It is preferable that the vinyl monomer B and the anionic monomer orcationic monomer be added to the system in which the vinyl monomer A ispolymerized when the conversion of the vinyl monomer A has reached 70%or more.

Alternatively, the polymer particles with protrusions on the surfacethereof can be prepared as follows:

Polymer particles with a smaller particle size and a narrower particlesize distribution than the polymer particles to be made are prepared touse as core particles. On the thus prepared core particles, the vinylmonomer A is polymerized to grow a polymer on the surface of the coreparticles to prepare polymer particles with a narrow particle sizedistribution. Protrusions can be formed on the thus prepared polymerparticles in the same manner as mentioned above.

The core particles can prepared by polymerizing the vinyl monomer A orother monomers, but must be insoluble in the above-mentioned hydrophilicorganic liquid.

Polymer particles with a narrow particle size distribution can beprepared from the vinyl monomer A by controlling the polymerizationreaction at the initial stage thereof.

The term "narrow particle size distribution" here means such a particlesize distribution of particles that the volume mean diameter dv thereofis 1≦dv≦15 (μm), and the ratio of the volume mean diameter dv to thenumber mean diameter dn thereof, that is, dv/dn, is 1≦dv/dn≦1.20, whenmeasured by Coulter counter made by Coulter Electronics Co., Ltd., usinga 100 μm thick aperture tube, in an automatic measurement mode with themeasurement conditions such as an aperture current set automatically,for measuring more than 30,000 particles. It is preferable that thevalue obtained when no particles are incorporated in the counter, whichcorresponds to the value obtained by noise, be deducted from the valueobtained from the above measurement.

In order to use the polymer particles in a toner for use inelectrophotography, which is capable of producing high quality images,the volume mean diameter dv thereof must be 15 μm or less, but when thevolume mean diameter dv is less than 1 μm, the handling of the polymerparticles is extremely difficult because the polymer particles are inthe form of dry powder.

A toner comprising the polymer particles which have a particle sizedistribution as broad as dv/dn>1.20 wherein dv is the volume meandiameter, and dn is the number mean diameter, is not capable ofdeveloping digital latent electrostatic images with high quality, andimages developed by such a toner are not uniform particularly in thequality of the reproduction of dot images. Furthermore, when such atoner is stored in a development unit, the particle size thereof tendsto be changed and the life of the toner tends to be shortened while itis stored.

As mentioned previously, when vinyl monomer A is polymerized, thepolymerization is conducted in the presence of a polymeric dispersingagent in a hydrophilic organic liquid or in a mixture of a hydrophilicorganic liquid and water, in which the vinyl monomer is soluble, but inwhich a polymer formed from the vinyl monomer swells or is substantiallyinsoluble, so that as soon as a polymer is formed from the vinyl monomerA, it is separated from the hydrophilic organic liquid. As a result,polymer particles with a narrow particle size distribution are formed.

When the polymerization is initiated, a polymeric dispersing agentserving as a dispersion stabilizer is dissolved in the hydrophilicorganic liquid, and the vinyl monomer A is then dissolved in themixture, with the oxygen in the polymerization system being replaced byan inert gas.

In the above, there are two cases with respect to the timing for theaddition of an initiator. In one case, an initiator is added to thepolymerization system and the temperature of the polymerization systemis thereafter raised to initiate the polymerization. In the other case,the temperature of the polymerization system is raised first, and thenan initiator is added to the polymerization system to initiate thepolymerization.

In the former case, the polymerization occurs slightly in the presenceof the initiator while the oxygen in the polymerization system is beingreplaced with an inert gas, while in the latter case, it is possiblethat the vinyl monomer A is polymerized by heat polymerization becauseof the elevation of the temperature of the polymerization system beforethe addition of an initiator.

By the above-mentioned initial polymerization, a polymer with a lowmolecular weight is formed in the form of a liquid, not in the form ofparticles. The thus formed polymer has an adverse effect on the initialformation of polymer core particles, by which the particle sizedistribution are broadened or fine polymer particles are formed.

In the above-mentioned first case, in which an initiator is added to thepolymerization system and the temperature of the polymerization systemis thereafter raised to initiate the polymerization, it is alsoimportant to hinder the initiation of the polymerization reaction asmuch as possible by cooling the polymerization system before theelevation of the temperature of the reaction mixture.

In the above-mentioned second case, in which the temperature of thepolymerization system is raised first, and then an initiator is added tothe polymerization system to initiate the polymerization, it isimportant to cool the polymerization system before the elevation of thetemperature thereof.

Furthermore, it is desirable that the oxygen contained in thepolymerization system be replaced by an inert gas at the initiation ofthe polymerization. It is preferable that the content of oxygen in thepolymerization system be not more than 1.0 vol. %, more preferably notmore than 0.1 vol. %. In case the replacement of oxygen by an inert gasis imperfect, a low-molecular weight reaction product formed in a traceamount tends to become fine particles so that the particle sizedistribution is broadened.

In the above-mentioned first case, the polymerization is initiated whenthe elevation of the temperature of the polymerization system isstarted. In the above-mentioned second case, the polymerization isinitiated when the initiator is added.

The previously mentioned, initially formed core particles are swollenwith a hydrophilic organic liquid or with an unreacted monomer, so thatthe initial core particles are unstable in many cases. When such coreparticles aggregate or are combined, the particle size distribution isbroadened, so that polymer particles with the desired particle sizedistribution cannot be obtained.

Therefore, as mentioned previously, core particles may be added to thepolymerization system prior to the initiation of the polymerization tocontrol the number of polymer particles to be formed. However, polymerparticles can be newly formed in addition to the core particles when anewly formed polymer do not fit with the core particles in terms of thecompatibility, polarity, and reactivity thereof.

In the present invention, the initial core particles can be stablyformed by controlling the concentration of the vinyl monomer A at theinitialization of the polymerization. The number of the core particlesformed can also be controlled. For this purpose, it is preferable thatthe concentration of the vinyl monomer A in the hydrophilic organicliquid at the initiation of the polymerization be such a concentrationthat 10 parts by weight or less, more preferably 5 parts by weight orless, of the vinyl monomer A, are added to 100 parts by weight of thehydrophilic organic liquid.

In order to cause the core particles to further grow, and to increasethe concentration of the polymer particles to be formed, 10 to 100 partsby weight, preferably 20 to 50 parts by weight, of the vinyl monomer Amay be further added to 100 parts by weight of the hydrophilic organicliquid.

The vinyl monomer A may be added, either in one lot or in separate lots,to the polymerization system. In order to perform stable polymerization,it is preferable to add the vinyl monomer A in separate lots, with thevinyl monomer A being diluted with the hydrophilic organic liquid tosome extent.

In the present invention, the initially formed core particles can besynthesized stably by controlling the polymerization rate at theinitiation of the polymerization within a predetermined range.

Stable core particles can be caused to grow by a successive growthreaction, with the particle size distribution maintained. Furthermore,the number mean diameter of the polymer particles can be controlled bycontrolling the polymerization rate in the initial stage of thepolymerization.

The polymerization rate can be controlled by various methods, such asthe method of controlling the initial concentration of the vinyl monomeras mentioned previously, a method of controlling the concentration of aninitiator employed at the initiation of polymerization, a method ofemploying an initiator which has a desired decomposition rate at theinitiation of polymerization, and a method of controlling thetemperature for polymerization to obtain the required decompositiontemperature for an initiator. These methods can be used in combination.

When the concentration of an initiator employed at the initiation ofpolymerization is controlled, it is preferable that the concentration ofthe initiator be such a concentration that the amount of the initiatoris 0.1 parts by weight or less, more preferably 0.05 parts by weight orless, to 100 parts by weight of the vinyl monomer to produce the polymerparticles in a stable and reproducible manner.

In order to increase the growth rate of the core particles formed, toproceed with the polymerization reaction to a high degree ofpolymerization, and also to obtain a polymer with a desired molecularweight, it is required to add an initiator in an amount of 0.1 parts byweight or more to 100 parts by weight of the unreacted vinyl monomer Ain the polymerization system in which the core particles have alreadybeen formed, thereby causing the polymerization reaction to furtherproceed.

The initiator employed in the above polymerization may be the same asthat employed in the formation of the core particles or may be differentfrom that initiator. A plurality of initiators may also be used incombination.

When a plurality of initiators with different decomposition rates isemployed, a polymer with a broad molecular weight distribution can beobtained. Furthermore, in accordance with the degree of the proceedingof the polymerization, initiators may be added in separate lots.

When an initiator to be added is in the form of powder, it is preferableto dissolve the initiator in the hydrophilic organic liquid employedbefore it is added to the polymerization system.

As an initiator which is used when the conversion of the monomer isbelow a predetermined range at the initiation of polymerization, aninitiator which is decomposed at a relatively high temperature should beused. More specifically, it is preferable to employ an initiator whichhas a half-life period of 10 hours and a decomposition temperature above80° C., during a period in which the degree of conversion of the vinylmonomer to a polymer is 10% or less. When core particles are formed in apolymerization system with a relatively small polymerization rate andthen the polymerization is moved onto the next polymerization step forforming polymer particles, polymer particles can be formed stably withexcellent reproducibility.

In order to increase the growth rate of the core particles formed, tocause the polymerization to proceed to a high degree of polymerization,and to obtain a polymer with a desired molecular weight, it ispreferable to employ an initiator having a relatively low decompositiontemperature. More specifically, it is preferable to employ an initiatorwith a half-life period of 10 hours and a decomposition temperature ofnot more than 80° C. to cause the further polymerization reaction toproceed quickly.

A plurality of initiators with a half-life period of 10 hours and adecomposition temperature of not more than 80° C. may be used incombination. When a plurality of initiators with different decompositionrates is used, a polymer with a broad molecular weight distribution canbe obtained, and also polymer particles with a narrow particle sizedistribution can be obtained. Furthermore, in accordance with the degreeof the proceeding of the polymerization, initiators may be added inseparate lots.

When the polymerization is initiated at a required polymerizationtemperature, it is preferable that the polymerization be conducted at atemperature at which an initiator employed in the polymerization systemis provided with a half-life period of 100 hours or more, core particlesbe formed with a relatively small polymerization rate in a stablemanner, and the polymerization be moved onto the next polymerizationstep for forming polymer particles.

In order to cause the polymerization reaction to proceed quickly, thepolymerization temperature may be gradually increased in such a mannerthat the half-life period of an initiator changes in the range of 100 to1 hour, or increased quickly when the conversion of the vinyl monomer toa polymer has reached a certain level.

It is preferable that a cross-linking agent be introduced into thepolymerization system in a ratio of 3 parts by weight of thecross-linking agent to 100 parts by weight of the vinyl monomer A in aperiod from the time of the initiation of polymerization through thetime when the degree of conversion of the vinyl monomer A to a polymeris low. When the ratio of the amount of a cross-linking agent to theamount of the vinyl monomer A exceeds the above-mentioned ratio, anaggregation tends to be formed in the polymerization system.

In case it is required to add a cross-linking agent further, it ispossible to add a cross-linking agent with a ratio of 10 parts by weightor less of the cross-linking agent to 100 parts by weight of theunreacted vinyl monomer A remaining in the polymerization system, whenthe conversion of the vinyl monomer A to a polymer is increased to arelatively high degree.

As a matter of course, when the previously mentioned growth reaction isconducted on polymer particles having a smaller particle size than thatof polymer particles to be finally formed, and a narrower particle sizedistribution than that of the polymer particles to be finally formed, itis possible to add a cross-linking agent with a ratio of 10 parts byweight or less of the cross-linking agent to 100 parts by weight of theunreacted vinyl monomer A remaining in the polymerization system.

The amount of such a cross-linking agent component can be determined byrefluxing polymer particles placed in a filter in a solvent in which thepolymer component of the polymer particles is soluble, and obtaining thecross-linking agent component as an insoluble component through afilter, or by dissolving the polymer particles in the above-mentionedsolvent with the addition of an auxiliary agent for filtration thereto,filtering or centrifuging the mixture to separate the cross-linkingagent component therefrom.

Further, in the present invention, a chain transfer agent can be usedtogether the vinyl monomer A.

A chain transfer agent can be used with a ratio of 0.001 to 3 parts byweight to 100 parts by weight of the vinyl monomer A. In particular,when a chain transfer agent is added to the polymerization system beforethe initiation of polymerization, the molecular weight of the initiallyformed polymer can be controlled so that the size of the polymerparticles separated can be controlled.

To be more specific, with respect to the core particles which are formedat the initial stage of the polymerization, the solubility and swellingperformance thereof within the polymerization system are determined bythe molecular weight of the polymer formed, and the molecular weight ofthe polymer has significant effects on the merging and aggregation ofthe initially formed core particles. The size of the initially formedcore particles depend upon the kind of chain transfer agent employed andthe amount of a chain transfer agent used.

When a chain transfer agent is added to the polymerization system afterthe formation of core particles, the chain transfer agent serves tocontrol the molecular weight of polymer particles to be formed so as toimpart the desired viscoelastic characteristics to the polymerparticles. When a cross-linking component is added to introduce it intothe polymer particles, and a chain transfer agent is also added, it isconsidered that the chain transfer agent has a surprising effect ofimparting excellent dispersing stability on the polymerization system.

It has also been discovered that the amount of a cross-linking agentcomponent employed and the amount of a chain transfer agent employedhave a significant effect on the molecular weight and molecular weightdistribution of a polymer formed.

It is considered that protrusions which are formed on the surface of thepolymer particles as will be discussed in more detail later are producedby the formation of a copolymer from a vinyl monomer B and an ionicmonomer, with the copolymer being formed within the polymer particlesand coming out toward the surface of the polymer particles. Therefore,it is considered that the formation of the protrusions is significantlyinfluenced by the cross-linking structure of the polymer particles whichserve as a matrix body for the protrusions, the viscoelastic propertiesof the polymer particles, the remaining unreacted vinyl monomer A, thevinyl monomer B, and other ionic monomers as will be discussed later.

In order to form protrusions on the surface of polymer particlesprepared from a polymerization system containing the vinyl monomer A, ifnecessary, with the addition of a cross-linking agent and a chaintransfer agent thereto, it is required to produce a polymer which isincompatible with a polymer prepared from the vinyl monomer A as themain component, within the above-mentioned polymer particles or near thesurface of the polymer particles.

After various investigations, the inventors of the present inventionhave discovered that a copolymer of a cationic monomer or an anionicmonomer, and a vinyl monomer B which will be mentioned later, issuitable for the incompatible polymer in view of the differences in thecompatibility and hydrophilic nature between the two polymers. Morespecifically, the inventors have discovered that, for the above purpose,it is of great importance that the polymer obtained from the vinylmonomer B have a higher glass transition point than that of a polymerprepared from the vinyl monomer A as the main component, and that it isan indispensable condition for forming protrusions on the surface ofpolymer particles that a relatively hard polymer with a polarityslightly different from that of a relatively soft polymer is formed fromwithin the soft polymer, with the above-mentioned condition being met.

As a matter of fact, for the formation of the protrusions on the surfaceof the polymer particles, in addition to the above-mentionedindispensable conditions, it is required to select appropriateconditions for the degree of cross-linking of the polymer prepared fromthe vinyl monomer A as the main component, the molecular weight andmolecular weight distribution of the polymer particles, the swelling ofthe polymer particles in a hydrophilic organic liquid, the vinyl monomerB, the temperature for the polymerization, and the solubility of aninitiator.

To be more specific, the vinyl monomer B and an anionic monomer or acationic monomer may be added to the polymerization system when theconversion of the vinyl monomer A to a polymer is increased to a certainextent and the growth of the polymer particles slows down. In this case,it is desirable that the vinyl monomer B and an anionic monomer or acationic monomer be diluted with a hydrophilic organic liquid in orderto prevent the aggregation of the polymer particles and to maintain thestability of the polymerization system. Furthermore, in this case, thehydrophilic organic liquid employed for the above-mentioned dilution maybe, either the same hydrophilic organic liquid as employed in theformation of polymer particles by the polymerization of the vinylmonomer A, or different from that. The incompatibility of the polymerfor the protrusions, which are formed near the surface of the polymerparticles, and the size, number and shape of the protrusions can beadjusted by utilizing the magnitude of the polarity of the hydrophilicorganic liquid employed for the dilution.

When necessary, the diluted vinyl monomer B and the ionic monomer can beadded either in one lot or in separate lots, or can be added gradually,to the polymerization system, whereby the stability of thepolymerization system and the properties of the protrusions can becontrolled.

Furthermore, by setting the temperature of the polymerization systemwhen the vinyl monomer B and the ionic monomer are added thereto at atemperature different from the temperature at which the vinyl monomer Ais polymerized, the swelling properties of the polymer particlesprepared from the monomer A as the main component can be changed,whereby the properties of the protrusions can also be controlled.

In order to improve the stability of the polymerization system,polymeric dispersing agents, surfactants, finely-divided inorganicparticles, pigments, and water-soluble inorganic compounds may be addedto the polymerization system when the diluted vinyl monomer and anionicmonomer or cationic monomer are added thereto.

In order to cause the polymerization reaction to proceed smoothly, it isdesirable to add an initiator. The initiator may be the same initiatoras employed in the polymerization of the vinyl monomer A or differentfrom the initiator.

In many cases, the thus formed protrusions are in the shape of part of asubstantial sphere or oval with a minimized surface energy. Inparticular, when the polymer particles with such protrusions on thesurface thereof are used in a toner for use in electrophotography, it ispreferable that the polymer particles have protrusions in theabove-mentioned shape on the surface thereof, and the ratio of theaverage height h of the protrusions from the surface of the polymerparticles to the average diameter D of the polymer particles which donot include the protrusions, that is, h/D, be 1/50≦h/D ≦ 1/2, and morepreferably the ratio of the surface area of the polymer particlesoccupied by the protrusions to the entire surface of the polymerparticles be 1/20 or more.

In the case of a toner comprising polymer particles with h/D < 1/50,which are extremely close to spherical particles, the fluidity thereofis good, but the toner particles considerably aggregate when reserved athigh temperatures, and have poor triboelectric chargeability.Furthermore, when a toner comprising such polymer particles is used inpractice, a large amount of toner remains on a photoconductor when tonerimages are transferred from the photoconductor to a transfer sheet, sothat it is extremely difficult to remove the remaining toner from thesurface of the photoconductor in a cleaning step, particularly by usinga cleaning blade.

In contrast, in the case of a toner comprising polymer particles withh/D> 1/2, the toner have the same characteristics as those of aconventional dry toner. However, the toner comprising the above polymerparticles are poor in the characteristics required for toner prepared bya conventional crushing method, such as fluidity, and image transferperformance. Furthermore, the toner has the shortcomings that it ispulverized by force generated within a development unit, and theparticle size distribution is changed, and accordingly thecharacteristics of the toner are changed.

The average height h of the protrusions from the surface of the polymerparticles is the average length of the perpendicular from the tips ofthe protrusions to the outer surface of the spherical polymer particles,directed to the center thereof, and the ratio of the surface area of thepolymer particles occupied by the protrusions to the entire surface ofthe polymer particles is expressed by the ratio of the total area of thebottoms of the protrusions on the surface of the spherical polymerparticles, which bottoms are substantially circular or oval, to theentire surface area of the polymer particles, which is supposed not tohave such protrusions on the surface thereof, in a microscopicphotograph taken by a scanning electron microscope.

A toner for use in electrophotography comprising polymer particleshaving such a shape exhibits high fluidity with excellent replenishmentperformance in a practical electrophotographic copying machine. Further,such a toner has excellent anti-blocking performance so that the tonerparticles thereof do not aggregate when preserved at high temperatures,and exhibits excellent triboelectric chargeability even when stirred foran extended period of time and preserved at high temperatures andhumidities. Furthermore, the toner has excellent image transferperformance, and the amount of the toner which remains on the surface ofa photo-conductor after image transfer is extremely small, so that thecleaning performance thereof is extraordinarily good. Such cleaningperformance cannot be obtained by a conventional toner comprisingspherical toner particles.

The formation of the protrusions of a copolymer can be confirmed bypreparing an ultra-thin plate sample of the obtained polymer particleswith a thickness of about several hundreds Å, for instance, by use of aglass knife or a diamond knife, and if necessary, by dyeing theultra-thin plate sample, for instance, with osmium tetroxide, and byinspecting the differences of the contrast of the protrusions in theultra-thin plate sample by a transmission type electron microscope.

In addition to the above, the formation of the protrusions can beconfirmed by surface analysis methods, using, for instance, an infraredmicroscope for FTIR, Raman spectrum, X-ray photoelectron spectroscopy(XPS), secondary ion mass spectroscopy (SIMS), and scanning transmissiontype electron microscope (STEM).

Examples of a hydrophilic organic liquid which is used when preparing apolymer which is made from the vinyl monomer A as the main component,and for preparing a copolymer which is used for forming the protrusionsmade from the vinyl monomer B, and an anionic monomer or a cationicmonomer, are as follows: alcohols such as methyl alcohol, ethyl alcohol,modified ethyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutylalcohol, t-butyl alcohol, s-butyl alcohol, t-amyl alcohol, 3-pentanol,octyl alcohol, benzyl alcohol, cyclohexanol, furfuryl alcohol,tetrahydrofurfuryl alcohol, ethylene glycol, glycerin, and diethyleneglycol; and ether alcohols such as methyl cellosolve, cellosolve,isopropyl cellosolve, butyl cellosolve, ethylene glycol monomethylether, ethylene glycol monoethyl ether, diethylene glycol monomethylether, and diethylene glycol monoethyl ether. These organic liquids canbe used alone or in combination.

Organic liquids other than the above-mentioned alcohols and etheralcohols can be used in combination with the above-mentioned alcoholsand ether alcohols, whereby the polymerization conditions can beadjusted by changing the solubility parameter (SP) value of the employedhydrophilic organic liquid under the conditions that the formed polymerparticles are insoluble in the organic liquids, so that the particlesize of the polymer particles formed can be controlled, and theformation of new polymer particles can be hindered.

Examples of the organic liquids to be used in combination with theabove-mentioned alcohols and ether alcohols are hydrocarbons such ashexane, octane, petroleum ether, cyclohexane, benzene, toluene andxylene; halogenated hydrocarbons such as carbon tetrachloride,trichloroethylene, and tertrabromoethane; ethers such as ethyl ether,dimethyl glycol, trioxane, and tetrahydrofuran; acetals such asmethylal, and diethyl acetal; ketones such as acetone, methyl ethylketone, methyl isobutyl ketone, and cyclohexane; esters such as butylformate, butyl acetate, ethyl propionate, and cellosolve acetate; acidssuch as formic acid, acetic acid and propionic acid; sulfur- ornitrogen-containing organic compounds such as nitropropene,nitrobenzene, dimethylamine, monoethanolamine, pyridine, dimethylsulfoxide, and dimethylformamide; and water.

The polymerization may be conducted in a solvent comprising any of theabove-mentioned hydrophilic liquids as the main component in thepresence of any of the following ions:

SO₄ ²⁻, SO₃ ²⁻, NO₃ ⁻, NO₂ ⁻, PO₄ ³⁻, Cl⁻, Na⁺, K⁺, Mg²⁺,

Ca²⁺, and other inorganic ions.

Furthermore, when a vinyl monomer with a relatively large polarity and asolvent or a mixed solvent with a SP value which is far from that of thevinyl monomer are employed at the initial stage of the polymerization,that is, at the stage of forming core particles, the core particlesseparated have a small particle size, and by adding another solventthereto, the merging of the core particles can be promoted, whereby theparticle size and the particle size distribution can be adjusted.

Furthermore, the average particle size, the particle size distributionof the formed polymer particles, and the properties of the protrusionscan be changed by changing the kind of mixed solvent employed and thecomposition thereof at the initiation of polymerization, during thepolymerization reaction, at the formation of the protrusions, and at thefinal stage of the polymerization.

Examples of a polymeric dispersing agent which is used for preparing apolymer which is made from the vinyl monomer A as the main component,and which is also used for forming the protrusions which are made fromthe vinyl monomer B, and an anionic monomer or a cationic monomer are asfollows: (1) homopolymers and/or copolymers of (a) acids such as acrylicacid, methacrylic acid, α-cyanoacrylic acid, α-cyanomethacrylic acid,itaconic acid, crotonic acid, fumaric acid, maleic acid and maleicanhydride; (b) hydroxyl-group-containing acrylic monomers such asβ-hydroxyethyl acrylate, β-hydroxyethyl methacrylate, β-hydroxypropylacrylate, β-hydroxypropyl methacrylate, γ-hydroxypropyl acrylate,γ-hydroxypropyl methacrylate, 3-chloro-2-hydroxypropyl acrylate,3-chloro-2-hydroxypropyl methacrylate, diethylene glycol monoacrylicester, diethylene glycol monomethacrylic ester, glycerin monoacrylicester, glycerin mono-methacrylic ester, N-methylolacrylamide, N-methylolmethacrylamide; (c) vinyl alcohols and ethers of vinyl alcohols such asvinyl methyl ether, vinyl ethyl ether, vinyl propyl ether; (d) esters ofvinyl alcohols and carboxyl-group-containing compounds such as vinylacetate, vinyl propionate, and vinyl butyrate; (e) acrylamide,methacrylamide, diacetone acrylamide, and methylol compounds thereof;(f) acid chlorides such as acrylic acid chloride, and methacrylic acidchloride; and (g) nitrogen-containing or nitrogen-containingheterocyclic-group-containing compounds such as vinyl pyridine, vinylpyrrolidone, vinyl imidazole, and ethyleneimine; (2) polyoxyethylenecompounds such as polyoxyethylene, polyoxypropylene, polyoxyethylenealkyl amine, polyoxypropylene alkyl amine, polyoxyethylene alkyl amide,polyoxypropylene alkyl amide, polyoxyethylene nonyl phenyl ether,polyoxyethylene lauryl phenyl ether, polyoxyethylene stearyl phenylester, polyoxyethylene nonyl phenyl ester; (3) cellulose derivativessuch as methyl cellulose, hydroxyethyl cellulose, and hydroxypropylcellulose; and (4) copolymers of any of the above-mentioned hydrophilicmonomers, and a phenyl-group-containing monomer such as styrene,α-methylstyrene, and vinyltoluene, and derivatives thereof, or acrylicacid derivatives or methacrylic acid derivatives such as acrylonitrile,methacrylonitrile, and acrylamide.

An appropriate polymeric dispersing agent can be selected from thesepolymeric dispersing agents in accordance with a hydrophilic organicliquid employed, and also in accordance with the timing for producingpolymer particles made from the vinyl monomer A as the main component,or for producing protrusions on the surface of the polymer particles.However, an appropriate polymeric dispersing agent is selectedparticularly from the viewpoints of the necessity for high affinity forthe surface of polymeric particles and high adsorption propertiesthereto and also for high affinity for the hydrophilic organic liquidand high solubility therein in order to sterically prevent the mergingof the polymeric particles.

Furthermore, a polymeric dispersing agent with a molecular chain with anappropriate length, preferably having a molecular weight of 10,000 ormore, is employed in order to enhance the steric repulsion among thepolymer particles. However, when the molecular weight of a polymericdispersing agent is excessively high, the viscosity of the polymericdispersing agent is too high to handle and to stir, and the polymericdispersing agent cannot always be present uniformly on the surface ofthe polymer particles formed. Therefore care must be taken not to usesuch a polymeric dispersing agent.

It is also effective for stabilizing the polymer particles to have anyof the above-mentioned monomers for producing the polymeric dispersingagents coexist with the vinyl monomers for producing the polymerparticles in the polymerization system.

For stabilizing the polymer particles and for obtaining an appropriateparticle size distribution efficiently, it is also effective to use anyof the following materials: finely-divided particles, preferably with aparticle size of 1 μm or less, of metals such as cobalt, iron, nickel,aluminum, copper, tin, lead, and magnesium, and alloys of these metals;finely-divided particles of anionic surfactants such as higher alcoholsulfuric esters, alkylbenzene sulfonates, α-olefinic sulfonates, andphosphoric esters; cation surfactants of an amine salt type such asalkylamine salts, aminoalcohol fatty acid derivatives, polyamine fattyacid derivatives; cationic surfactants of a quaternary ammonium salttype such as alkyltrimethy ammonium salts, dialkyldimethyl ammoniumsalts, alkyldimethylbenzyl ammonium salts; non-ionic surfactants such asfatty acid amide derivatives, and polyhydric alcohol derivatives; andampholytic surfactants of an amino acid type, such as alanine type[dodecyldi(aminoethyl)glycine and di(octylaminoethyl)glycine, andampholytic surfactants of a betaine type.

Generally, the amount of the polymeric dispersing agent to be employeddiffers depending upon the kind of polymerizable monomer forsynthesizing polymer particles. However, it is preferable that theamount of the polymeric dispersing agent be 0.1 to 10 parts by weight,more preferably 1 to 5 parts by weight, to 100 parts by weight of thehydrophilic organic liquid. When the concentration of the polymericdispersing agent in the hydrophilic organic liquid is low, polymerparticles with a relatively large particle size can be obtained, whilewhen the concentration of the polymeric dispersing agent is high,polymer particles with a relatively small particle size can be obtained.However, even if the concentration of the polymeric dispersing agentexceeds 10 parts by weight to 100 parts by weight of the hydrophilicorganic liquid, it does not have much effect on the reduction of theparticle size of the polymer particles to be formed.

The above-mentioned polymeric dispersing agents, and optionally, thefinely-divided particles of inorganic materials, pigments, andsurfactants mentioned above, are necessary for the production of polymerparticles made from the vinyl monomer A as the main component. Theseagents may also be used when producing the protrusions by polymerizationby adding them to a solution of the vinyl monomer B, and an anionic orcationic monomer, in order to prevent the merging of the protrusionsformed on the surface of the polymer particles.

The core particles formed at the initial stage of polymerization arestabilized by the polymeric dispersing agent which is distributed to thehydrophilic organic liquid and to the surface of the polymer particles,and is in equilibrium with them. However, when a large amount ofunreacted vinyl monomer A is present in the hydrophilic organic liquid,the core particles are swollen to some extent by the unreacted vinylmonomer A and becomes adhesive. As a result, the core particles overcomethe steric repulsion generated by the polymeric dispersing agent andaggregate.

When an extremely large amount of the vinyl monomer A is present incomparison with the amount of the hydrophilic organic liquid, thepolymer formed is completely dissolved in the vinyl monomer A, so thatthe polymer formed does not separate out before the polymerizationproceeds to some extent. In this case, the separated polymer is in theform of an adhesive lump. As a matter of course, there is somelimitation on the amount of the vinyl monomer A relative to the amountof the hydrophilic organic liquid. The relative amount of the vinylmonomer A may differ, depending upon the kind of the hydrophilic organicliquid, but generally it is preferable that the amount of the vinylmonomer A be not more than about 100 parts by weight, more preferablynot more than 50 parts by weight, to 100 parts by weight of thehydrophilic organic liquid.

The vinyl monomer A for use in the present invention is soluble in thehydrophilic organic liquid. Specific examples of the vinyl monomer A areas follows: styrene, and styrene derivatives such as o-methylstyrene,m-methylstyrene, p-methylstyrene, α-methylstyrene, p-ethylstyrene,2,4-dimethylstyrene, p-n-butylstyrene, p-tert-butylstyrene,p-n-hexylstyrene, p-n-octylstyrene, p-n-nonylstyrene, p-n-decylstyrene,p-n-dodecylstyrene, p-methoxystyrene, p-phenylstyrene, p-chlorostyreneand 3,4-dichlorostyrene; s-methyl fatty acid monocarboxylic ester suchas methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate,propyl acrylate, n-octyl acrylate, dodecyl acrylate, lauryl acrylate,2-ethylhexyl acrylate, stearyl acrylate, 2-chloroethyl acrylate, phenylacrylate, methyl α-chloroacrylate, methyl methacrylate, ethylmethacrylate, propyl methacrylate, n-butyl methacrylate, isobutylmethacrylate, n-octyl methacrylate, dodecyl methacrylate, laurylmethacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, phenylmethacrylate, dimethylaminoethyl methacrylate and diethylaminoethylmethacrylate; derivatives of acrylic acid and methacrylic acid such asacrylonitrile, methacrylonitrile, and acrylamide; and halogenated vinylcompounds such as vinyl chloride, vinylidene chloride, vinyl bromide,and vinyl fluoride. These monomers may be used alone or in combination.Furthermore, as the vinyl monomer A for use in the present invention, amixture of any of the above-mentioned monomers in an amount of 50 wt. %or more, and one or more other monomers which can be copolymerized withthe aforementioned monomer.

As a cross-linking component for use in the polymer particles,cross-linking agents with two or more polymerizable double bonds areemployed.

It is preferable that the amount of the cross-linking agent to be addedbe not more than 3 parts by weight, more preferably not more than 1.5parts by weight, to 100 parts by weight of the vinyl monomer A in theperiod from the initiation of polymerization thorough the moment theconversion of the vinyl monomer A reaches 10%.

When the degree of polymerization conversion of the vinyl monomer Aexceeds 10%, if necessary, it is preferable that the amount of thecross-linking agent to be added be not more than 10 parts by weight to100 parts by weight of the remaining vinyl monomer A. The cross-linkingagent may be added in one lot or in lots. It is preferable that thecross-linking agent be added in lots in accordance with the degree ofthe proceeding of polymerization.

The previously mentioned cross-linking agents can be used together withthe vinyl monomer B, and an anionic or cationic monomer when forming theprotrusions on the surface of the polymer particles, whereby theformation of the protrusions can be promoted and protrusions made of across-linked polymer can be formed.

The concentration of the cross-linking agent at the initial stage ofpolymerization must be controlled below a certain level. This is becauseif the concentration of the cross-linking agent is above a certain levelwhen the initial core particles are being separated at the initial stageof polymerization, or when the polymeric dispersing agent is stablyabsorbed on the particles, cross-linking structures are formed among thecore particles, so that the stabilization of the core particles isextremely hindered.

Once the core particles are stabilized, the successive steps of thegrowth reaction on the surface of the core particles to form polymerparticles, which is carried out by the swelling of the core particles inthe vinyl monomer A, and the polymerization of the vinyl monomer A onthe surface of the core particles, and the formation of protrusions onthe surface of the polymer particles, proceed smoothly without beinghindered by the cross-linking agent.

Examples of the cross-linking agent, which are preferably employed inthe present invention, are as follows: aromatic divinyl compounds suchas divinyl-benzene, divinyl naphthalene, and derivatives thereof;carboxylic acid esters such as ethylene glycol diacrylate, ethyleneglycol dimethacrylate, triethylene glycol diemthacrylate, tetraethyleneglycol diemthacrylate, 1,3-butylene glycol dimethacrylate,trimethylolpropane triacrylate, trimethylolpropane trimethacrylate,1,4-butanediol diacrylate, neopentyl glycol diacrylate, 1,6-hexanedioldiacrylate, pentaerythritol diacrylate, pentaerythritol triacrylate,pentaerythritol tetraacrylate, pentaerythritol dimethacrylate,pentaerythritol trimethacrylate, pentaerythritol tetramethacrylate,glycerol dimethacrylate, glycerol diacrylate, and1,1,1-trishydroxymethylethane diacrylate; and all divinyl compounds andcompounds having three or more vinyl groups such as N,N-divinyl-aniline,divinyl ether, divinylsulfide, divinylsulfone. These cross-linkingagents can be used alone or in combination.

There is no particular limitation on the chain transfer agent for use inthe present invention. However, the so-called polymerization retardersand polymerization inhibitors, which reduce not only the molecularweight of the polymer particles to be formed, but also thepolymerization rate thereof, cannot be used in the present invention.

Examples of the chain transfer agent, which are preferably employed inthe present invention, are as follows: halogenated hydrocarbons such ascarbon tetrachloride, carbon tetrabromide, ethyl acetate dibromide,ethyl acetate tribromide, ethylbenzene dibromide, ethane dibromide andethane dichloride; diazothioether; hydrocarbons such as benzene,ethylbenzene and isopropylbenzene; alkylmercaptans such as tertiarydedocylmercaptan and n-dodecylmercapatan; thioalcohols such asmercaptoethanol and mercaptopropanol; disufides such asdiisopropylxanthogenedisulfide, dimethylsulfide and diethylsulfide;pentaerythritol tetrathioglycolate, octyl thiopropionate, thioglycollicacid, and esters thereof; thioglycerin; thioaldehydes such asthioethylaldehyde, thiopropylaidehyde, thiooctylaldehyde andthiododecyl-aldehyde; azobenezene derivatives; naphthalene derivatives;and nuclear-substituted aromatic compounds.

As the vinyl monomer B for forming protrusions, one or more monomers canbe selected from the previously mentioned vinyl monomer A and monomersfor forming the previously mentioned polymeric dispersing agent,although the vinyl monomer B is not limited to the above monomers.

However, when a vinyl monomer with a relatively high polarity isselected as the vinyl monomer B, it is preferable to use the vinylmonomer in combination with a vinyl monomer with a relatively low parityin order that the formed polymer be not dissolved in the hydrophilicorganic liquid.

Further, it is required that the vinyl monomer B, when polymerized,provide a polymer having a higher glass transition point than that of apolymer obtained by polymerizing the vinyl monomer A as the maincomponent. Specific data for the glass transition points of suchpolymers are shown, for instance, in "Polymer Handbook" 3rd EditionSection VI, P 209 (A Willy Inter Science Publication).

Examples of an anionic vinyl monomer which is used in combination withthe vinyl monomer B for forming the protrusions include an unsaturatedcarboxylic acid monomer, an unsaturated sulfonic acid monomer, and anunsaturated phosphoric acid monomer.

Specific examples of the unsaturated carboxylic acid monomer are acrylicacid, methacrylic acid, crotonic acid, itaconic acid, and maleic acid;half esters such as monobutyl itaconic ester, monomethyl maleic ester,monobutyl maleic ester and monooctyl maleic ester; fumaric acid,citraconic acid, cinnamic acid, butene tricarbonic acid, 3-butenoicacid, 4-pentenoic acid, tetrahydroterephthalic acid; and anhydrides ofdibasic acids such as maleic anhydride, itaconic anhydride.

Specific examples of the unsaturated sulfonic monomer are styrenesulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid,3-sulfopropylmethacrylic ester, 3-sulfopropylacrylic ester,bis-(3-sulfopropyl)itaconic ester, sulfuric monoester of2-hydroxyethylmethacrylic acid, sulfuric monoester of2-hydroxyethylacrylic acid, allylsulfosuccinic acid, octylallylsulfosuccinate, vinylsulfonic acid, 2-sulfoethylmethacrylate,2-sulfoethylacrylate, and salts thereof.

Specific example of the unsaturated phosphoric acid monomer are asfollows:

vinylphosphonic acid,

vinylphosphate,

acid phosphoxyethylmethacrylate,

acid phosphoxyethylacrylate,

3-chloro-2-acid phosphoxypropylmethacrylate,

3-chloro-2-acid phosphoxypropylacrylate,

acid phosphoxypropylmethacrylate,

acid phosphoxypropylacrylate,

bis(methacryloxyethyl)phosphate,

diphenyl-2-acryloyloxyethylphosphate,

diphenyl-2-methacryloyloxyethylphosphate,

dibutyl-2-methacryloyloxyethylphophate,

dibutyl-2-acryloyloxyethylphosphate,

dioctyl-2-methacryloyloxyethylphosphate,

dioctyl-2-acryloyloxyethylphosphate, and

mono-(2-methacryloyloxyethyl) acid phosphate.

Examples of a cationic vinyl monomer which is used in combination withthe vinyl monomer B for forming the protrusions include a (meth)acrylateof an aliphatic alcohol including an amino group or an alkyl group;(meth)acrylamide; (meth)acrylate and (meth)acrylamide with the nitrogenatom being substituted with a mono- or di-alkyl-group; vinyl compoundssubstituted with a heterocyclic group including a nitrogen atom in theheterocyclic group; N,N-diallylalkylamine; styrene derivatives having amono- or di-alkyl group; vinyl ethers having a mono- or di-alkylaminogroup; and compounds prepared by making the above amine compoundsquaternary compounds.

Examples of the (meth)acrylate of an aliphatic alcohol including anamino group or an alkyl group are as follows:

N,N-dimethylaminoethyl(meth)acrylate,

N,N-diethylaminoethyl(meth)acrylate,

3-dimethylaminophenyl(meth)acrylate,

N,N-dimethylaminopropyl(meth)acrylate,

N,N-diethylaminopropyl(meth)acrylate, and

N-methylaminoethyl(meth)acrylate.

Examples of the (meth)acrylate and (meth)acrylamide with the nitrogenatom being substituted with a mono- or di-alkyl-group are as follows:

acrylamide,

N-butylacrylamide,

N,N-dibutylacrylamide,

piperidine acrylamide,

N-(N',N'-dimethylamidoethyl)acrylamide,

N-(N',N'-dimethylaminoethyl)methacrylamide,

methacrylamide,

N-butylmethacrylamide,

N,N-dimethylacrylamide,

N-octadecylacrylamide,

N-(N',N'-diethylaminoethyl)acrylamide,

N-(N',N'-diethylaminoethyl)methacrylamide,

N-(N',N'-dimethylaminopropyl)acrylamide,

N-(N',N'-dimethylaminopropyl)methacrylamide,

N-(N',N'-diethylaminopropyl)acrylamide,

N-(N',N'-diethylaminopropyl)methacrylamide,

diacetone acrylamide,

N-hydroxymethylacrylamide,

N-methylaminoethylacrylamide, and

N-methylaminomethacrylamide.

Examples of the vinyl compounds substituted with a heterocyclic groupcontaining a nitrogen atom in the heterocyclic group includevinylpyridine, vinylpyrrolidone, 2-methyl-5-vinylpyridine and2-ethyl-5-vinylpyridine.

Examples of the N,N-diallylalkylamine include N,N-diallylmethylamine,and N,N-allylethylamine.

Examples of the styrene derivatives having a mono- or di-alkyl groupinclude N,N-dimethylaminomethyl styrene, N,N-dimethylaminoethyl styreneand N,N-diethylaminoethyl styrene.

Examples of the vinyl ethers having a mono- or di-alkylamino groupinclude 2-dimethyaminoethyl vinyl ether, and 2-diethylaminoethyl vinylether.

Furthermore, compounds prepared by making the above-mentioned compoundsquaternary compounds can also be used. Examples of an agent for makingthe compounds quaternary compounds include the following conventionalagents: a dialkyl sulfate with the number of carbon atoms in the alkylgroup being 4 or less, an alkyl sulfonate of an alkylsulfonic acid or anarylsufonic acid, with the number of carbon atoms in the alkyl groupbeing not more than 18, such as methanesulfonic acid, benzenesulfonicacid, and toluenesulfonic acid; a compound having a halogenated benzylgroup such as benzyl chloride, and benzyl bromide; and a compound havinga halogenated alkyl group with not more than 18 carbon atoms.

An ampho-ionic monomer having cationic and anionic properties can alsobe used in combination with the vinyl monomer B for forming theprotrusions on the surface of the polymer particles. Examples of theampho-ionic monomer include the following:

N,N-dimethyl-N-methacryloxyethyl-N-(3-sulfo)propyl-ammoniumbetaine,

N,N-dimethyl-N-methacrylamidopropyl-N-(3-sulfopropyl)-ammoniumbetaine,

1-(3-sulfopropyl)-2-vinylpyridiniumbetaine,

N-(vinylbenzyl)taurine,

N-methyl-N-(vinylbenzyl)taurine,

N-(isopropenylbenzyl)taurine,

N-(2-hydroxy-3-alloxypropyl)taurine,

2-[N-(2-hydroxy-3-alloxypropyl)]taurine, and

N-(2-hydroxy-3-alloxypropyl)alanine.

These anionic or cationic vinyl monomers can be added together with thevinyl monomer B to the polymerization system when the conversion of thevinyl monomer A has increased to some extent and polymer particles havebeen formed, so that the growth of the particle size has slowed down,preferably when the conversion of the vinyl monomer A has reached 70% ormore.

However, it is not always necessary to add the anionic or cationicmonomer together with the vinyl monomer B to the polymerization system.The anionic or cationic monomer may be added either before or after theaddition of the vinyl monomer B. Furthermore, the anionic or cationicmonomer may be added in one lot or in lots.

A copolymer synthesized from the vinyl monomer B and the anionic orcation monomer as the main components has a relatively large polarity,so that in order to prevent the synthesized copolymer from beingdissolved in the hydrophilic organic liquid, the amount of the anionicor cationic monomer is determined in accordance with the kind of thevinyl monomer B and the amount of the vinyl monomer B employed.Preferably 1 to 30 parts by weight of the anionic or cationic monomer isemployed for 100 parts by weight of the vinyl monomer B. The amount ofthe anionic or cationic monomer may of course be changed from the aboverange when necessary.

Examples of an initiator usually used for the polymerization of thevinyl monomer A, the vinyl monomer B, and the anionic or cationicmonomer include peroxides such as benzoyl peroxide, lauryl peroxide,di-t-butylperoxide, cumenehydroperoxide, t-butyl-peroctoate,t-butylperoxy-2-ethylhexanoate; and azo compounds such asazobisisobutyronitrile, 2,2-azobis(2,4-dimethylvaleronitrile),2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), anddimethyl-2,2'-azobisisobutylate.

Examples of an initiator having a relatively large polarity includeamidine derivatives such as 2,2'-azobis(2-amidinopropane)dihydrochloride,2,2'-azobis-(N,N'-dimethylene-isobutylamidine),2,2'-azobis(N,N-dimethyleneisobutylamidine)dihydrochloride. Thesecompounds may be used in the form of an aqueous solution. In addition,initiators such as carboxylic-acid-containing azo compounds, forexample, 4,4'-azobis(4-cyanopentanoic acid); persulfate-based initiatorssuch as potassium perfulfate, and ammonium perfulfate; and initiatorscomprising any of the above initiators and sodium thiosulfate or aminemay be used. The above-mentioned initiators can be used alone or incombination.

Examples of a peroxide-based initiator with a half-life period of 10hours above 80° C., which belong to a group of initiators havingrelatively high decomposition temperatures and are used during theperiod in which core particles are formed and stabilized at the initialstage of polymerization are as follows:

1,1-bis(t-butylperoxy)cyclohexane,

t-butylperoxylaurate,

cyclohexanoneperoxide,

t-butylperoxyisopropylcarbonate,

2,2'-bis(t-butylperoxy)octane,

2,2'-bis(t-butylperoxy)butane,

n-butyl-4,4'bis(t-butylperoxy)octane,

2,2'-bis(t-butylperoxy)butane,

n-butyl-4,4'-bis(t-butylperoxy)valerate,

methyl ethyl ketone peroxide,

dicumylperoxide,

2,5-dimethyl-2,5-di(t-butylperoxy)hexane,

t-butylcumylperoxide,

di-t-butylperoxide,

2,5-dimethyl-2,5-di(t-butylperoxy)hexane,

2,5-dimethylhexane-2,5-dihydroperoxide,

cumene hydroperoxide, and

t-butyl hydroperoxide.

Examples of an azo initiator with a half-life period of 10 hours above80° C. are as follows:

1,1'-azobis(cyclohexane-1-carbonitrile),

1-{(1-cyano-1-methylethyl)azo}formamide,

2-phenylazo-4-methoxy-2,4-dimethylvaleronitrile,

2,2'-azobis{2-methyl-N-(1,1-bis(hydroxymethyl)ethyl}propionamide,

2,2'-azobis{2-methyl-N-(2-hydroxyethyl)-propionamide},

2,2'-azobis(2-methylpropionamido)dihydrate,

2,2'-azobis(2,4,4-trimethylpentane), and

2,2'-azobis(2-methylpropane).

Examples of a peroxide-based initiator with a half-life period of 10hours at 80° C. or less, which belong to a group of initiators havingrelatively low decomposition temperatures and are used after theformation of core particles are as follows:

acetylcyclohexyl sulfonylperoxide,

isobutylperoxide,

cumyl peroxineododecanoate,

diisopropyl peroxydicarbonate,

diallyl peroxydicarbonate,

di-n-propyl peroxydicarbonate,

dimyristyl peroxydicarbonate,

cumyl peroxyneohexanate,

di(2-ethoxyethyl)peroxydicarbonate,

di(methoxyisopropyl)peroxydicarbonate,

di(2-ethylhexyl)peroxycarbonate,

t-hexylperoxyneodecanoate,

di(3-methyl-3-methoxybutyl)peroxydicarbonate,

t-butylperoxyneodecanoate,

t-hexylperoxyneohexanoate,

t-butylperoxyneohexanoate,

2,4-dichlorobenzoylperoxide,

t-hexylperoxypivalate,

3,5,5-trimethylhexanoylperoxide,

octanoylperoxide,

decanoylperoxide,

lauroylperoxide,

cumylperoxyloctanoate,

succinic acid peroxide,

acetylperoxide,

t-butylperoxy(2-ethylhexanoate),

m-toluoylperoxide,

benzoylperoxide, and

t-butylperoxyisobutylate.

Examples of an azo initiator with a half-life period of 10 hours at 80°C. or less are as follows:

2,2'-azobis(2-methoxy-2,4-dimethylvaleronitrile),

2,2'-azobis-cyclopropylpropionitrile),

2,2'-azobis-2,4-dimethylvaleronitrile),

2,2'-azobisisobutyronitrile,

2,2'-azobis(2-methylbutyronitrile),

2,2'-azobis(2-methyl-N-phenylpropionamidine)dihydrochloride,

2,2'-azobis{N-(4-chlorophenyl)-2-methylpropionamidine}dihydrochloride,

2,2'-azobis{2-methyl-N-(phenylmethyl)-propionamidine}dihydrochloride,

2,2'-azobis(2-methylpropionamidine)dihydrochloride,

dimethyl-2,2'-azobisisobutylate,

4,4'-azobis(4-cyano valeic acid),

2,2'-azobis{2-(hydroxymethyl)propionitrile},

2,2'-azobis[2-{2-(5-methyl-2-imidazoline-2-yl)}propane]dihydrochloride,

2,2'-azobis{2-(3,4,5,6-tetrahydropyrimidine-2-yl)propane}dihydrochloride,

2,2'-azobis[2-{1-(2-hydroxyethyl)-2-imidazolin-2-yl}propane]dihydrochloride,and

2,2'-azobis[2-methyl-N-{1,1-bis(hydroxymethyl)-2-hydroxyethyl}propionamide].

In addition to the above-mentioned peroxide-based initiators and azoinitiators, persulfate-based initiators can be employed if thedecomposition temperatures thereof are in a desired range.

If the polymerization rate is controlled by controlling thepolymerization temperature in order to form stable core particles at theinitial stage of polymerization, and the following initiators are used,it is preferable that the polymerization be conducted at the temperatureat which the following initiators provide a half-life period of 10 hourswhen the conversion of the polymers is 10% or less:

    ______________________________________                                                            Temperature (°C.)                                  ______________________________________                                        t-hexylperoxyneohexanoate                                                                           32.5                                                    2,4-dichlorobenzylperoxide                                                                          33.0                                                    t-butylperoxypivalate 38.0                                                    octanoylperoxide      45.0                                                    decanoylperoxide      45.0                                                    lauroylperoxide       46.0                                                    cumylperoxide         48.8                                                    m-toluoylperoxide     56.0                                                    benzoylperoxide       56.6                                                    t-butylperoxyisobutylate                                                                            61.0                                                    t-butylperoxylaurate  73.0                                                    t-butylperoxyacetate  85.0                                                    (In the case of azo initiators)                                               2,2-azobis(2-cyclopropylpropionitrile)                                                              26.5                                                    2,2'-azobis(2,4-dimethylvaleronitrile)                                                              37.0                                                    2,2'-azobisisobutyronitrile                                                                         50.0                                                    2,2'-azobis(2-methylbutyronitrile)                                                                  52.5                                                    1,1'-azobis(cyclohexane-1-carbonitrile)                                                             72.0                                                    1-{(1-cyano-1-methylethyl)azo}formamide                                                             86.0                                                    azodi-t-octane        89.0                                                    4,4'-azobis(4-cyanopentanic acid)                                                                   53.0                                                    2,2'-azobis(2-cyanopropanol)                                                                        60.0                                                    ______________________________________                                    

It is preferable that after the formation of stable core particles, thepolymerization be caused to proceed at a temperature above theabove-mentioned respective temperatures. The above-mentioned initiatorscan be employed in amount of 0.1 to 10 parts by weight to 100 parts byweight of the vinyl monomer.

The conditions for the polymerization for producing a copolymer from thevinyl monomer A which is employed as the main component, morespecifically, the concentrations and mixing ratios of the polymericdispersing agent and the vinyl monomer in the hydrophilic organicliquid, are set in accordance with the desired mean particle size, andparticle size distribution of the polymer particles to be produced.Generally, the concentration of the polymeric dispersing agent isincreased in order to decrease the mean particle size of the polymerparticles, and the concentration of the polymeric dispersing agent isdecreased in order to increase the mean particle size of the polymerparticles.

On the other hand, in order to obtain the polymer particles with anarrow particle size distribution, the polymerization is conducted in areaction chamber under the conditions that the temperature of the vinylmonomer A is set low, and the reaction mixture is heated to atemperature in accordance with the decomposition temperature of aninitiator employed, with the reaction mixture being stirred to produce auniform flow in the reaction chamber. Since the temperature of thereaction mixture at an initial stage of polymerization has a significanteffect on the particle size of the core particles to be formed, it isdesirable that the reaction mixture be heated to a polymerizationtemperature after the monomer is added thereto, and the initiator beadded thereto in the form of a solution which is prepared by dissolvingthe initiator in a small amount of a solvent.

When the polymerization is conducted, it is required that oxygencontained in the atmosphere in the reaction chamber be completelyreplaced by an inert gas such as nitrogen or argon. If the replacementof the oxygen by such an inert gas is insufficient, polymer particleswith an extremely small particle size tend to be formed.

In order to perform the polymerization with high conversion, it isnecessary that the polymerization be conducted for 5 to 40 hours.However, the polymerization can be terminated when the desired particlesize and particle size distribution are obtained, or the rate ofpolymerization can be increased by adding an initiator in lotssuccessively, by changing the polarity of a hydrophilic organic liquidemployed, or by conducting the polymerization under high pressure.

In the case where dyed polymer particles are obtained after thepolymerization, the polymer particles obtained by the above-mentionedpolymerization may be directly dyed, or the polymer particles may besubjected to a separation process for removing therefrom unnecessaryparticles, the remaining monomer, and the polymeric dispersing agent byan operation such as sedimentation, centrifugation, and washing bydecantation, to obtain the polymer particles in the form of a polymerslurry, and the polymer slurry is dyed. It is better not to remove thepolymeric dispersing agent, since the dyeing system is highly stable,and unnecessary aggregation of the polymer particles can be avoided inthe presence of the polymeric dispersing agent.

When the polymer particles obtained by the above-mentionedpolymerization are used as dyed polymer particles for a toner forelectrophotography, the polymer particles are dyed as follows:

The polymer particles are dispersed in an organic solvent in which thepolymer particles are insoluble. Before or after dispersing the polymerparticles in the organic solvent, there is dissolved in theabove-mentioned solvent a dye with a solubility of [D₁ ] in the solvent,and a solubility of [D₂ ] in the polymer of the polymer particles, andwith a relationship of [D₁ ]/[D₂ ]≦0.5, preferably with a relationshipof [D₁ ]/[D₂ ]≦0.2, whereby the polymer particles are dyed with the dye.Thereafter the solvent is removed from the above mixture. Dyed polymerparticles with the dye being diffused or penetrating deeply into theinside thereof can be efficiently produced by the above-mentionedmethod. The thus obtained dyed polymer particles are hereinafterreferred to as the colored particles.

In the above, the respective solubilities [D₁ ] and [D₂ ] are to bemeasured at 25° C., and the solubility [D₂ ] in the polymer is definedin the same manner as in the case of the solubility of [D₁ ] in thesolvent. Namely, the solubility [D₂ ] in the polymer means a maximumamount of the dye that can be dissolved in a compatible state in a unitamount of the polymer. The dissolved state or a separated state of thedye in the polymer can be easily identified by a microscope.

The solubility of a dye in a polymer can also be assessed by an indirectmethod instead of the above-mentioned direct observation of the state ofthe dye in the polymer. In the indirect method, the dye is dissolved ina solvent in which the polymer is highly soluble, and the solubility ofthe dye in the solvent is measured. The thus measured solubility of thedye is defined as the solubility of the dye in the polymer.

As the dyes for use in the present invention, any conventional dyes canbe employed as long as the above-mentioned solubility relationship canbe met. In general, water-soluble dyes such as cationic dyes and anionicdyes are not suitable for use in the present invention because theproperties thereof are significantly changeable depending upon theambient conditions and when they are used in the toner, the resistivityof the toner tends to be decreased and therefore the image transferratio tends to be decreased. For this reason, vat dye, disperse dye, andoil-soluble dye are preferable for use in the present invention. Ofthese dyes, oil-soluble dye is most suitable for use in the presentinvention. As a matter of course, several dyes can be used incombination for obtaining a desired color tone.

The weight ratio of the dye to the polymer particles to be dyed can beselected as desired, depending upon the desired color tone. However,generally it is preferable that the amount of the dye be in the range of1 to 50 parts by weight to 100 parts by weight of the polymer particlesto be dyed.

In the present invention, when an alcohol having a relatively high valueof solubility parameter (hereinafter referred to as SP value), such asmethanol and ethanol, is employed as a solvent for dying and astyrene-acrylic resin having a SP value of 9 is used as the material forthe polymer particles, for example, the following dyes can be employed:

C.I. Solvent Yellow (6, 9, 17, 31, 35, 100, 102, 103, 105),

C.I. Solvent Orange (2, 7, 13, 14, 66),

C.I. Solvent Red (5, 16, 17, 18, 19, 22, 23, 143, 145, 146, 149, 150,151, 157, 158),

C.I. Solvent Violet (31, 32, 33, 37),

C.I. Solvent Blue (22, 63, 78, 83-86, 91, 94, 95, 104),

C.I. Solvent Green (24, 25), and

C.I. Solvent Brown (3, 9).

In addition, the following commercially available dyes can be employed:

Aizen Sot dyes such as Yellow-1, 3, 4, Orange-1, 2, 3, Scarlet-1, Red-1,2, 3, Brown-2, Blue-1, 2, Violet-1, Green-1, 2, 3, and Black-1, 4, 6, 8(made by Hodogaya Chemical Co., Ltd.); Sudan dyes such as Yellow-140,150, Orange-220, Red-290, 380, 460, and Blue-670 (made by BASF);Diaresin, Yellow-3G, F, H2G, HG, HC, HL, Orange-HS, G, Red-GG, S, HS, A,K, H5B, Violet-D, Blue-J, G, N, K, P, H3G, 4G, Green-C, and Brown-A(made by Mitsubishi Chemical Industries, Ltd.); Oil Color, Yellow-3G,GG-S, #105, Orange-PS, PR, #201, Scarlet-#308, Red-5B, Brown-GR, #416,Green-BG, #502, Blue-BOS, IIN, and Black-HBB, #803, EE, EX (OrientChemical Industries, Ltd.); Sumiplast Blue GP, OR, Red FB, 3B, andYellow FL7G, GC (made by Sumitomo Chemical Co., Ltd.); Kayaron,Polyester Black EX-SF300, and Blue A-2R of Kayaset Red-B (made by NipponKayaku Co., Ltd.).

The applicable dyes are not limited to the above.

As the organic solvents for dying the polymer particles with any of theabove dyes, it is preferable to employ solvents in which the polymerparticles are not dissolved, or in which the polymer particles slightlyswell with the solvents. More specifically it is preferable to employorganic solvents with a difference between the SP value of the solventsand that of the polymer particles be 1.0 or more, more preferably 2.0 ormore, or a mixed solvent of water and an organic solvent. Morespecifically, it is preferable to employ an alcohol having a high SPvalue such as methanol, ethanol or n-propanol, or an organic solventhaving a low SP value such as n-hexane n-propane in combination withstyrene-acrylic resin particles.

However, when the difference in the SP value between the organic solventand the polymer particles is too large, the wetting of the polymerparticles with the solvent is so poor that the polymer particles are notappropriately dispersed in the organic solvent. Therefore, it ispreferable that the SP value difference be in the range of 2 to 5.

In the present invention, the dying is carried out, for example, bydispersing the polymer particles in the above-mentioned organic solventin which an appropriate dye is dissolved, and stirring the dispersionunder the conditions that the temperature of the dispersion is keptbelow the glass transition temperature of the polymer of the polymerparticles, whereby the polymer particles can be dyed sufficientlywithout causing the aggregation of the polymer particles. For stirringthe dispersion of the dye and polymer particles, a conventional stirrersuch as homomixer or magnetic stirrer can be employed.

Alternatively, the dyed resin particles can be obtained by directlyadding the dye to a slurry comprising an organic solvent and polymerparticles which are dispersed in the organic solvent, which is obtained,for example, at the completion of the dispersion polymerization process,and stirring the mixture under the above-mentioned conditions.

In any of the above-mentioned processes, when the temperature at whichthe polymer particles and the dye-containing solvent are mixed andstirred is above the glass transition temperature of the resinparticles, there may be the case where the polymer particles aggregatewhile stirred.

There is no particular limitation on the method of drying a dyed slurry,but it is preferable to remove the remaining dye from the slurry, andthe polymer particles be separated from the slurry by filtration anddried under reduced pressure. Alternatively the slurry is directlydried, without the filtration of the polymer particles. In the presentinvention, the colored particles obtained by drying the slurry underreduced pressure or at room temperature after the separation of thepolymer particles by filtration substantially do not aggregate and havesubstantially the same particle size distribution as that of the polymerparticles prior to the dyeing process.

Polymer particles with protrusions on the surface thereof themselveshave high fluidity, excellent anti-blocking performance when allowed tostand at high temperature, excellent high-impact properties when molded,high triboelectric properties, low temperature-dependent coefficient ofthermal expansion, and excellent optical properties and dyeability.However, the characteristics of the polymer particles can be furtherimproved by treating the polymer particles with a surfactant with afluoroalkyl group, primarily by forming salts by the reaction of thesurfactant with anionic or cationic functional groups which are mainlylocated in the protrusions formed on the surface of the polymerparticles.

Examples of the surfactant with a fluoroalkyl group, which arepreferably in the present invention are as follows:fluoroalkylcarboxylic acids with 2 to 10 carbon atoms, and metal saltsthereof, di-sodium perfluorooctane sulfonyl glutamate, sodium3-[fluoroalkyl (C₈ -C₁₁)oxy-1-alkyl (C₃ -C₄) sulfonate, sodium3-[ω-fluoroalkanolyl (C₆ -C₈)-N-ethylamino-1]-propanesulfonate,fluoroalkyl (C₁₁ -C₂₀) carboxylic acid and metal salts thereof,perfluoro alkyl carboxylic acid (C₇ -C₁₃) and metal salts thereof,perfluoroalkyl (C₄ -C₁₂) sulfonic acid and metal salts thereof,perfluorooctane sulfonic acid diethanolamide,N-propyl-N-(2-hydroxyethyl) perfluorooctane sulfonamide, perfluoroalkyl(C₆ -C₁₀) sulfonamide propyl trimethyl ammonium salt, perfluoroalkyl (C₈-C₁₀)-N-ethylsulfonly glycine salt, and monoperfluoroaklyl (C₈ -C₁₆)ethyl phosphoric acid ester.

Examples of a commercially available anionic surfactant for use in thepresent invention include SURFLON S-111, S-112, S-113 (made by AsahiGlass Co., Ltd.), FLUORAD FC-93, FC-95, FC-98, FC-129 (made by Sumitomo3M Limited), UNIDYNE DS-101, DS-102 (made by Daikin Industries, Ltd.),MEGAFAC F-110, F-120, F-113, F-191, F-812, and F-833 (made by DainipponInk & Chemicals, Incorporated), EFTOP EF-102, 103, 104, 105, 112, 123A,123B, 306A, 501, 201, 204 (made by Tohkem Products Corporation), andFTERGENT F-100, F-150 (Neos Co., Ltd.).

Examples of a cationic surfactant for use in the present inventioninclude aliphatic primary, secondary and tertiary amine salts having afluoroalkyl group; an aliphatic quaternary ammonium salt such asperfluoroalkyl (C₆ -C₁₀) sulfonamide propyltrimethyl ammonium salt;benzalkonium salt; benzethonium salt; pyridinium salt; and imidazoliniumsalt.

The following cationic surfactants in Table 1 are particularlypreferable for use in the present invention:

                  TABLE 1                                                         ______________________________________                                        C.sub.8 F.sub.17 SO.sub.2 NH(CH.sub.2).sub.3 N.sup.+ (CH.sub.3).sub.2         CH.sub.2 COO.sup.-                                                            C.sub.8 F.sub.17 CONH(CH.sub.2).sub.3 N.sup.+ (CH.sub.3).sub.3 I.sup.-        C.sub.8 F.sub.17 SO.sub.2 NH(CH.sub.2).sub.3 N.sup.+ (CH.sub.3).sub.3         I.sup.-                                                                        ##STR1##                                                                      ##STR2##                                                                      ##STR3##                                                                      ##STR4##                                                                      ##STR5##                                                                      ##STR6##                                                                      ##STR7##                                                                      ##STR8##                                                                     ______________________________________                                    

Examples of a commercially available anionic surfactant for use in thepresent invention include SURFLON S-121 (made by Asahi Glass CO., LTD.),FLUORAD FC-135 (made by Sumitomo 3M Limited), YUNIDYNE DS-202 (made byDaikin Industries, LTD.), MEGAFAC F-150, and F-824 (made by DainipponInk & Chemicals, Incorporated), EFTOP EF-132 (made by Tohkem ProductsCorporation), and FTERGENT F-300 (Neos Co., Ltd.).

The treatment of the polymer particles by such a surfactant can beconducted by mixing a slurry of the polymer particles with a hydrophilicorganic liquid in which such a surfactant is dissolved, or with amixture of a hydrophilic organic liquid and water in which such asurfactant is dissolved. In order to promote the treatment reaction,when necessary, the above mixture may be heated, or an auxiliaryswelling agent with an appropriate solubility parameter (SP value) fordiffusing the surfactant into the inside of the protrusions formed onthe surface of the polymer particles may be added to the mixture.

When dyed or colored polymer particles are prepared, the above treatmentcan be carried out after the dyeing of the polymer particles.

When an unsaturated sulfonic acid monomer is used as an anionic monomerfor the formation of the protrusions on the surface of the polymerparticles and the above-mentioned treatment is conducted by use of acationic or anionic surfactant having a fluoroalkyl group, salts formedby neutralizing a primary, secondary or tertiary amine having afluoroalkyl group with an inorganic acid or an organic acid such asacetic acid, lactic acid, or citric acid, and quaternary ammonium saltshaving a fluoroalkyl group are particularly preferable as cationicsurfactants for the above-mentioned treatment.

When a (meth)acrylate or (meth)acrylamide having a primary, secondary ortertiary amino group, or in the form of a quaternary ammonium salt, isemployed as a cationic polymer for the formation of the protrusions onthe surface of the polymer particles, sulfonate type anionic surfactantssuch as fluoroalkylbenzene sulfonate; and surfactants having a sulfonicacid group such as fluoroaklylnaphthalene sulfonic acid, and formalincondensation products thereof, fluoroalkylsulfosuccinic acid estersalts, and fluoroalkylsulfoacetate are particularly preferable asanionic surfactants for the above-mentioned treatment.

The electric properties of a toner comprising the polymer particles thustreated by such surfactants are significantly improved in comparisonwith those of a toner comprising the polymer particles which are nottreated by any of the surfactants.

The above-mentioned improved electric properties are particularlyexhibited in a toner which comprises polymer particles of a polymer inwhich the combination of a functional group contained in the protrusionsand a functional group contained in a cationic or anionic surfactanthaving a fluoroalkyl group is a combination of a sulfonic acid group andan amine or quaternary ammonium salt.

In the present invention, a toner with releasability can be provided bycoating the surface of the above prepared colored polymer particles witha releasing agent or a binder agent in the form of finely-dividedparticles. To be specific, such coating of a releasing agent orfinely-divided binder agent particles is carried out as follows:

The above-mentioned colored polymer particles and a releasing agent orfinely-divided binder agent particles are mixed, whereby the releasingagent or finely-divided binder agent particles are caused to beuniformly deposited on the surface of the colored polymer particles, arefixed thereto, if necessary, with the application of heat or mechanicalenergy thereto.

By this coating treatment, a releasing agent or finely-divided binderagent particles can be firmly fixed to the surface of the coloredpolymer particles, so that a toner comprising the colored polymerparticles coated with such a releasing agent or finely-divided binderagent particles has high durability and anti-offset performance whenused in development by heat rollers, accordingly has high operationalperformance.

In the present invention, any releasing agents can be employed so longas they are capable of preventing the deposition of the toner on heatrollers and image transfer materials during thermal image fixing byusing heat rollers.

Examples of such releasing agents include polyolefins such aslow-molecular weight polyethylene, and polypropylene; and waxes.

Specific examples of waxes are vegetable waxes such as candelilla wax,carnauba wax, rice wax, and Japan wax; animal waxes such as bees wax,lanolin and spermaceti; mineral waxes such as montan wax, ceresine, andozocerite; petroleum waxes such as paraffin wax, microcrystalline waxand petrolatum; synthetic coal waxes such as mantanic acid wax, montanicester wax, montanic partially saponified ester wax and montanic softwax; and synthetic fat-and-oil type waxes such as Fischer-Tropsch wax;and hardened castor oil.

In addition, the following 12-hydroxystearic acid and derivativesthereof can be employed as releasing agents:

12-hydroxystearamide,

N-(2-hydroxyethyl)-12-hydroxystearamide,

N,N'-ethylenebis-12-hydroxystearamide,

N,N'-hexamethylenebis-12-hydroxystearamide,

N,N'-xylylenebis-12-hydroxystearamide,

methyl 12-hydroxystearate,

butyl 12-hydroxystearate,

propylene glycol=mono 12-hydroxystearate,

glycerine=mono 12-hydroxystearate,

ethylene glycol=mono 12-hydroxystearate,

glycerin=tri 12-acetoxystearate,

lithium 12-hydroxystearate, and

calcium 12-hydroxystearate.

The following fatty acid amides such as lauramide, stearamide, oleamide,erucamide, ricinolamide, 12-hydroxystearamide, and special fatty acidamides, can also be employed as the releasing agents.

Furthermore, the following fatty acid amide derivatives can be employedas the releasing agents:

N,N'-ethylenebislauramide,

N,N'-methylenebisstearamide,

N,N'-ethylenebisstearamide,

N,N'-ethylenebisoleamide,

N,N'-ethylenebisbehenamide,

N,N'-ethylenebis-12-hydroxystearamide,

N,N'-butylenebisstearamide,

N,N'-hexamethylenebisstearamide,

N,N'-hexamethylenebisoleamide,

N,N'-xylylenebisstearamide,

stearic acid monomethylol amide,

coconut fatty acid monoethanol amide,

stearic acid diethanol amide,

N-oleylstearamide,

N-oleyloleamide,

N-stearylstearamide,

N-stearyloleamide,

N-oleylpalmitamide,

N-stearylerucamide,

N,N'-dioleyladipamide,

N,N'-distearyladipamide,

N,N'-dioleylsebacamide,

N,N'-distearylsebacamide,

N,N'-distearylterephthalamide, and

N,N'-distearylisophthalamide.

Aliphatic amines, such as dodecylamine, tetradecylamine, octadecylamine,oleylamine, and dioctadecylamine, can also be employed as the releasingagents.

The following fatty acid esters of primary alcohols can also be employedas the releasing agents: methyl laurate, methyl myristate, methylpalmitate, methyl stearate, methyl coconut fatty acid, isopropylmyristate, butyl stearate, octadecyl stearate, and oleyl oleate.

The following fatty acid esters of polyhydric alcohols can also beemployed as the releasing agents: glycerin fatty acid ester such asglycerin=mono-stearate, glycerin=monooleate, and glycerin=docosanolate;sorbitan fatty acid esters such as sorbitan =monopalmitate,sorbitan=monostearate, sorbitan=tristearate and sorbitan=monooleate;propylene glycol fatty acid ester such as propyleneglycol=monopalmitate, and propylene glycol=monostearate; ethylene glycolfatty acid esters such as ethylene glycol =monostearate; andpolyoxyethylene fatty acid esters such as polyoxyethylene=monostearate.

Furthermore, the following compounds can be employed as the releasingagents: alkali metal salts and alkali earth metal salts of higher fattyacids, such as calcium stearate, aluminum stearate, magnesium stearate,and calcium palmitate, and zinc salts and aluminum salts of higher fattyacids; hydrazides of higher fatty acids such as hydrazide of palmiticacid, and hydrazide of stearic acid; p-hydroxianilides of higher fattyacids such as p-hydroxyanil of myristic acid, and p-hydroxyanilide ofstearic acid; β-diethylaminoethyl ester hydrochloride of higher fattyacids such as β-diethylaminoethyl ester hydrochloride of lauric acid,and β-diethylaminoethyl ester hydrochloride of stearic acid; fatty acidamide--formaldehyde condensation products such asstearamide--formaldehyde condensation product, andpalmitamide--formaldehyde condensation product; and halogenatedhydrocarbons such as chlorinated paraffin, and chlorinated propylene.

When the above-mentioned releasing agents are used in practice, thepreviously mentioned colored polymer particles are dispersed in aliquid, and the releasing agent in water or a hydrophilic organicliquid. In this case, it is preferably that the releasing agent bestably dispersed in the form of finely-divided particles in water or thehydrophilic organic liquid, and the previously mentioned colored polymerparticles and the releasing agent be not soluble in water or thehydrophilic liquid and that the liquid in which the colored polymerparticles are dispersed be compatible with water or the hydrophilicorganic liquid.

Such releasing agent dispersion liquids are commercially available andalso can be prepared, for example, by the following conventionalmethods:

(1) A releasing agent is dissolved in a solvent A in which the releasingagent is soluble to prepare a solution. This solution is added withstirring at high speed to a solvent B, which is compatible with solventA, but in which the releasing agent is not soluble, to precipitate thereleasing agent in the form of finely-divided particles, whereby adispersion liquid of the releasing agent is obtained.

(2) Hot water is added with stirring at high speed to a liquid in whicha releasing agent is fused to prepare a dispersion of the releasingagent. The dispersion is cooled to obtain a dispersion liquid of thereleasing agent.

(3) A releasing agent is mixed with a liquid C in which the releasingagent is insoluble in a dispersing apparatus such as a ball mill todisperse the releasing agent in the liquid, whereby a dispersion of thereleasing agent is obtained.

To the above prepared dispersion liquids, an ionic surfactant or anon-ionic surfactant, or a mixture of the two surfactants can be addedas a dispersion stabilizer.

It is preferable that the ratio of the volume mean particle size (R) ofthe colored polymer particles to the volume mean particle size (r) ofthe finely-divided particles of the releasing agent in the dispersionliquid, that is, R/r be 5 or more. When the ratio R/r is less than 5, itis not always easy to uniformly deposit the releasing agent on thesurface of the colored polymer particles and to firmly the releasingagent thereto, and accordingly, it becomes difficult to maintain uniformchargeability and durability when used as toner.

There is no particular limitation on the finely-divided particles of abinder agent for use in the present invention. The same resins as forthe above-mentioned colored polymer particles, for example,styrene-acrylic resin, polyester resin, and epoxy resin, can beemployed. The finely-divided particles of such resins can be produced bya dry fine pulverizing method using, for instance, a jet mill, or by awet fine pulverizing method using, for instance, a ball mill, sand mill,or colloid mill. The wet fine pulverizing method is preferable for usein the present invention, because the finely-divided particles of suchresins can be obtained in the form of a dispersion.

Such finely-divided particles of a binder resin can also be obtained bysuspension polymerization and also by emulsion polymerization. However,a soap-free emulsion polymerization is preferable because neither anemulsifier nor a dispersing agent is substantially contained in theresin particles produced.

The above-mentioned releasing agent or the finely-divided particles of abinder resin (hereinafter referred to as finely-divided binder resinparticles) can be deposited on the surface of the previously mentionedcolored polymer particles as follows:

A slurry of the colored polymer particles and a slurry of a releasingagent, if necessary, with the addition of finely-divided binder resinparticles thereto, are mixed and then dried, whereby the releasing agentcan be deposited on the surface of the colored polymer particles,together with the binder resin particles when added thereto. Foruniformly depositing the releasing agent, and the binder resin particleson the surface of the colored polymer particles and for obtainingparticles free from aggregation, it is preferable to conduct spraydrying, freezing drying, fluid bed drying, or medium fluid bed drying.

Alternatively, a releasing agent and finely-divided binder resinparticles can be deposited on the surface of the colored polymerparticles by utilizing the difference in the charges of the particles inthe dispersion liquid. This is the so-called hetero aggregation and canbe conducted so long as particles whose charged polarity is reversed orwhose quantity of charge is changed depending upon the pH of the mediumin which the particles are dispersed. Namely, the releasing agent andthe finely-divided binder resin particles can be deposited in the formof a uniform layer on the surface of the colored polymer particles byutilizing electrostatic force generated by electric charges withopposite polarities or a difference in potential, which can be generatedby adjusting the pH of the medium. In this deposition, the surfactantsand an ionic group of a dispersion stabilizer employed when producing areleasing agent in the form of finely-divided particles, and ionicgroups such as sulfuric acid group from potassium persulfate, and aminegroup from 2,2'-azobis(2-aminopropane)hydrochloride, which are formedfrom the fragments of an initiator employed for producing thefinely-divided resin particles, play an important role.

The so-called hetero aggregation can be carried out by use of thefollowing coagulating agents: inorganic electrolytes such as aluminumsulfate, basic aluminum chloride, sodium aluminate, ferric sulfate,ferrous sulfate, ferric chloride, calcium chloride, sulfuric acid,hydrochloric acid, carbonic acid, sodium carbonate, lime, electrolyticaluminum hydroxide, and electrolytic iron hydroxide; finely-dividedinorganic particles such as kaolin, bentonite, terra abla, fly ash, andactivated silicic acid; polymers with a molecular weight in the range of1000 to tens of thousands, such as sodium alginate, sodium salt ofcarboxymethyl cellulose (CMC), water-soluble aniline resinhydrochloride, polythiourea acetate, polyethylene imine, polyvinylbenzyltrimethyl ammonium chloride, starch, water-soluble urea resin, andgelatin; and polymers with a molecular weight in the range of severalmillions, such as sodium polyacrylate, copolymers of salts of maleicacid, poly(acrylamide)acrylic acid, polyvinyl pyridine copolymerhydrochloride, polyacrylamide, and polyoxyethylene.

A releasing agent and finely-divided binder resin particles can bedeposited in the form of a uniform layer on the surface of the polymerparticles by adjusting the electrostatic interaction between theparticles by neutralizing the ionic group on the surface of the polymerparticles by use of an ionic surfactant.

It is preferable that the amount of the releasing agent to be depositedon the surface of the colored polymeric particles be in the range of 0.3to 10 parts by weight, more preferably in the range of 0.5 to 5 parts byweight, to 100 parts by weight of the colored polymeric particles, inorder that the releasing agent exhibit its effect appropriately.

In the present invention, by firmly depositing the releasing agent andthe finely-divided binder resin particles on the surface of the coloredpolymer particles, the detachment of the releasing agent and thefinely-divided binder resin particles from the surface of the coloredpolymer particles can be prevented, so that the durability andreliability of a toner comprising such colored polymer particles can beimproved.

The releasing agent and the finely-divided binder resin particles can befixed to the surface of the colored polymer particles by heat treatmentor the application of mechanical energy thereto.

More specifically, when the releasing agent or the finely-divided binderresin particles are fixed to the surface of the colored polymerparticles by the application of mechanical energy thereto, mechanicalenergy is applied to a mixture of the colored polymer particles and thereleasing agent or to a mixture of the colored polymer particles and thefinely-divided binder resin particles, for instance, by stirring themixture with blades which are rotated at high speed, by bringing themixture into an air flow which are circulated at high speed, or bycausing the particles with each other or with a collision board.

Specific examples of a commercially available apparatus for theapplication of mechanical energy for the above-mentioned purpose includepulverizing apparatus with a reduced pulverizing air pressure which islower than that of a normal pulverizing air pressure such as "Angmill"(Trademark) (made by Hoshokawa Micron Corporation), and "Inpact Mill"(Trademark) (made by Pneumatic Mfg. Co., Ltd.), and other pulverizingapparatus such as "Hybridization System" (Trademark) (made by NaraMachinery Co., Ltd.), "Kryptron SystemKosmos" (Trademark) (made byKawasaki Heavy Industries, Ltd.), and an automatic mortar.

Furthermore, in the present invention, the above-mentioned apparatus forfixing the releasing agent or finely-divided binder resin particles tothe colored polymer particles may be used in order to deposit thereleasing agent or finely-divided binder resin particles on the coloredpolymer particles in a liquid. However, such fixing can be performedduring a drying process, for instance, by using a medium fluid bed dryer"MSD" (Trademark) (made by Nara Machinery Co., Ltd.) or a medium fluidbed dryer "Slurry Dryer" (Trademark) (made by Okawara Mfg. Co., Ltd.),by which drying and fixing of the releasing agent or finely-dividedbinder resin particles can be performed simultaneously.

When necessary, additives such as a fluidity improving agent and alubricant may be added to the thus produced toner of the presentinvention. Examples of the fluidity improving agent include hydrophobicsilica and metal oxides such as titanium oxide and alumina. Examples ofthe lubricant include finely-divided particles of polyvinylidenefluoride and zinc stearate.

The features of this invention will become apparent in the course of thefollowing description of exemplary embodiments which are given forillustration of the invention and are not intended to be limitingthereof.

EXAMPLE 1

The following components were placed in a glass reaction vessel equippedwith a condenser, a nitrogen-introducing tube, a pair of stainlessturbines, each having four blades slanted with a degree of 45°, with thediameter of the turbine being 2/3 the inner diameter of the reactionvessel, a motor for the stainless turbines, a dropping funnel, athermometer, and a syringe inlet:

    ______________________________________                                                        Parts by Weight                                               ______________________________________                                        Methanol          60                                                          Ethanol           20                                                          Distilled water   10                                                          Polyvinyl pyrrolidone                                                                            2                                                          (weight average molecular                                                     weight: 40,000)                                                               ______________________________________                                    

The above mixture was stirred at room temperature and the polyvinylpyrrolidone was completely dissolved in the mixture.

The reaction vessel was placed in a constant-temperature water bath bywhich the temperature of the reaction mixture can be controlled within arange of±0.1° C. Nitrogen was introduced into the reaction vesselthrough the nitrogen-introducing tube, with the reaction mixture beingcooled to 5° C. The concentration of oxygen in the gas phase in thereaction system was reduced to 0.1 vol. % or less by the replacement ofoxygen with the nitrogen by being monitored with a Galvanic-battery typeoxygen analyzer.

When the temperature of the reaction mixture was cooled to 5° C., thefollowing components were added to the reaction mixture through thedropping funnel:

    ______________________________________                                                          Parts by Weight                                             ______________________________________                                        Styrene             20                                                        Methyl acrylate     10                                                        Ethyl acrylate      10                                                        n-dodecylmercaptane 0.15                                                      Divinyl benzene (converted to                                                                     0.5                                                       the amount of the effective                                                   component as being 100%)                                                      ______________________________________                                    

The concentration of oxygen in the reaction system increased to 0.5 vol.%. The oxygen was replaced with nitrogen, so that the concentration ofoxygen in the reaction system was reduced to 0.1 vol. % or less.

The temperature of the constant-temperature water bath was elevated to65° C., and when the temperature of the reaction mixture reached 60° C.the stirring speed was set at 100 rpm, and a solution of an initiatorconsisting of the following components was added dropwise by a syringethrough the syringe inlet:

    ______________________________________                                                        Parts by Weight                                               ______________________________________                                        2,2'-azobis(2,4-dimethyl-                                                                       0.0016                                                      valeronitrile)                                                                Methanol          0.02                                                        ______________________________________                                    

The reaction mixture was transparent for about 15 minutes after theaddition of the solution of the initiator, but in about 15 minutes, thereaction mixture became milky white. The reaction mixture was thenallowed to stand for 30 minutes and became further milky white.

A solution composed of the following components was added dropwise tothe above milky white mixture through the dropping funnel over a periodof 15 minutes:

    ______________________________________                                                        Parts by Weight                                               ______________________________________                                        2,2'-azobis(2,4-dimethyl-                                                                       0.8                                                         valeronitrile)                                                                Methanol          10                                                          ______________________________________                                    

The polymerization was further continued for 5 hours and 30 minutes, anda mixture of the following components was added to the reaction mixturethrough a syringe:

    ______________________________________                                                         Parts by Weight                                              ______________________________________                                        α-thioglycerol                                                                             0.4                                                        1,3-butanediol methacrylate                                                                      0.6                                                        Methanol           5                                                          ______________________________________                                    

The polymerization was further continued for 10 hours, and part of thereaction mixture was then sampled by a syringe, with care being taken toavoid the evaporation of the liquid from the reaction mixture.

A small amount of hydroquinone was added to the sampled reaction mixtureto terminate the polymerization. The sampled reaction mixture was thendried at room temperature for 5 hours, and then dried at 50° C. underreduced pressure until the weight of a solid polymer obtained becameconstant. The conversion of the monomers to the obtained polymer wascalculated to be 79.2%, with the amounts of the dispersing agent and theinitiator employed taken into consideration.

The temperature of the reaction mixture was lowered to 20° C. bydecreasing the set temperature of the constant-temperature water bath,and a mixture of the following components for the formation ofprotrusions on polymer particles was added dropwise from the droppingfunnel over a period of 2 hours:

    ______________________________________                                                        Parts by Weight                                               ______________________________________                                        Methacrylamide propyl tri-                                                                       1                                                          methylammonium chloride                                                       Methyl methacrylate                                                                             19                                                          Methanol          40                                                          Distilled water    5                                                          ______________________________________                                    

When the dropwise addition of the above components was completed, thereaction mixture was stirred at a stirring speed of 70 rpm for 1 hour,with the temperature thereof raised to 50° C.

A mixture of the following components was then added dropwise from adropping funnel to the reaction mixture over a period of 30 minutes:

    ______________________________________                                                        Parts by Weight                                               ______________________________________                                        2,2'-azobisisobutyronitrile                                                                     0.4                                                         Methanol          7                                                           ______________________________________                                    

The polymerization reaction was continued at 50° C. for 3 hours, andthen the temperature of the reaction mixture was raised to 65° C.,taking 1 hour. The polymerization reaction was further continued for 20hours, whereby a milky white dispersion liquid was obtained.

Part of the milky white dispersion liquid was then sampled and a smallamount of hydroquinone was added to the sampled dispersion liquid toterminate the polymerization. The sampled dispersion was then dried atroom temperature for 5 hours, and then dried at 50° C. under reducedpressure until the weight of a solid polymer obtained became constant.The conversion of the monomers was found to have reached 98.7%, with theamounts of the dispersing agent and the initiator employed taken intoconsideration.

An extremely small amount of the milky white dispersion liquid wasdiluted by a large amount of distilled water, centrifuged, and thendispersed once again distilled water to remove unreacted components andthe dispersing agent therefrom, whereby purified polymer particles wereobtained.

The thus obtained polymer particles were inspected by a scanningelectron microscope. Polymer particles with a substantially uniformparticle size, with a plurality of hemispherical protrusions beingformed with substantially equal intervals therebetween on the surface ofthe polymer particles, were observed. No newly formed fine polymerparticles were found.

EXAMPLE 2

The following components were placed in the same glass reaction vesselas employed in Example 1:

    ______________________________________                                                        Parts by Weight                                               ______________________________________                                        2-propanol        70                                                          Distilled water   20                                                          Maleic anhydride - methyl                                                                       1.5                                                         vinyl ether copolymer                                                         (weight average molecular                                                     weight: 150,000)                                                              ______________________________________                                    

The above mixture was stirred at 70° C. for 5 hours, so that the maleicanhydride--methyl vinyl ether copolymer was partially esterified anddissolved in the reaction mixture.

The reaction vessel was placed in the same constant-temperature waterbath as employed in Example 1, and nitrogen was introduced into thereaction vessel through the nitrogen-introducing tube, with the reactionmixture being cooled to 5° C. When the concentration of oxygen in thegas phase in the reaction system was reduced to 0.1 vol. % or less bythe replacement of oxygen with the nitrogen as in Example 1, thefollowing components were added to the reaction mixture through thedropping funnel:

    ______________________________________                                                          Parts by Weight                                             ______________________________________                                        Styrene             30                                                        n-butyl methacrylate                                                                              5                                                         Methyl acrylate     15                                                        Carbon tetrachloride                                                                              0.1                                                       Ethylene glycol dimethacrylate                                                                    0.5                                                       ______________________________________                                    

The concentration of oxygen in the reaction system increased to 0.6 vol.%. The oxygen was replaced with nitrogen, so that the concentration ofoxygen in the reaction system was reduced to 0.1 vol. % or less.

The temperature of the constant-temperature water bath was elevated to70° C., and when the temperature of the reaction mixture reached 65° C.,the stirring speed was set at 75 rpm, and a solution of an initiatorconsisting of the following components was added dropwise over a periodof 15 minutes by a syringe through the syringe inlet:

    ______________________________________                                                        Parts by Weight                                               ______________________________________                                        2,2'-azobis(2,4,4-trimethyl-                                                                    0.45                                                        pentane)                                                                      2-propanol        5                                                           ______________________________________                                    

The reaction mixture became milky white about 10 minutes after theaddition of the solution of the initiator, and in about 15 minutes, thedegree of the milky white state was further intensified, so that theturbines in the reaction vessel became almost invisible.

The polymerization reaction was further continued for 3 hours, and thena solution composed of the following components was added dropwise tothe above milky white reaction mixture through the dropping funnel overa period of 15 minutes:

    ______________________________________                                                        Parts by Weight                                               ______________________________________                                        2,2'-azobis(2-methoxy-2,4-                                                                      0.75                                                        dimethylvaleronitrile)                                                        2-propanol        10                                                          ______________________________________                                    

With the temperature of the reaction mixture raised to 80° C., thepolymerization was further continued for 6 hours, and part of thereaction mixture was then sampled by a syringe, and the conversion ofthe monomers to the polymer was measured in the same manner as inExample 1. The result was that the conversion was 91.2%.

The temperature of the reaction mixture was lowered to 60° C., and amixture of the following components for the formation of protrusions onpolymer particles was separately added dropwise in nine separate lotsfrom the dropping funnel over a period of 3 hours:

    ______________________________________                                                      Parts by Weight                                                 ______________________________________                                        Methacrylic acid                                                                              1                                                             Styrene         9                                                             2-propanol      25                                                            ______________________________________                                    

With the temperature of the reaction mixture raised to 80° C., a mixtureof the following components was then added dropwise from a droppingfunnel to the reaction mixture over a period of 15 minutes:

    ______________________________________                                                        Parts by Weight                                               ______________________________________                                        2,2'-azobisisobutyronitrile                                                                     0.6                                                         2-propanol        10                                                          ______________________________________                                    

The polymerization reaction was continued at the same temperature for 10hours, whereby a milky white dispersion liquid was obtained.

The conversion of the monomers was measured in the same manner as inExample 1. The result was that the conversion was 99.3%.

An extremely small amount of the milky white dispersion liquid wasdiluted by a large amount of distilled water, centrifuged, and thendispersed once again distilled water to remove unreacted components andthe dispersing agent therefrom, whereby purified polymer particles wereobtained.

The thus obtained polymer particles were inspected by a scanningelectron microscope. Spherical polymer particles with a substantiallyuniform particle size, with a plurality of hemispherical protrusionsbeing formed with substantially equal intervals therebetween on thesurface of the polymer particles, were observed. No newly formed finepolymer particles were found.

EXAMPLE 3

A dispersion liquid of polymer particles with a conversion of 79.6%,without protrusions on the surface of the polymer particles, wasobtained in the same manner as in Example 1.

Part of the dispersion liquid was sampled, and the polymer particlestherein were inspected by a scanning electron microscope. It wasobserved that spherical polymer particles with a smooth surface, and auniform particle size were formed.

The temperature of the polymer dispersion liquid was lowered to 20° C.by decreasing the set temperature of the constant-temperature waterbath, and a mixture of the following components for the formation ofprotrusions on polymer particles was added dropwise from the droppingfunnel over a period of 2 hours:

    ______________________________________                                                        Parts by Weight                                               ______________________________________                                        Methacryloyloxy ethyl tri-                                                                       3                                                          methylammonium chloride                                                       Dimethylaminopropyl                                                                              1                                                          methacrylamide                                                                Methylmethacrylate                                                                              26                                                          Methanol          75                                                          ______________________________________                                    

When the dropwise addition of the above components was completed, withthe temperature of the reaction mixture raised to 50° C., the reactionmixture was stirred at a stirring speed of 70 rpm for 1 hour.

A mixture of the following components was then added dropwise from adropping funnel to the reaction mixture:

    ______________________________________                                                        Parts by Weight                                               ______________________________________                                        2,2'-azobisisobutyronitrile                                                                     0.5                                                         Methanol          8                                                           ______________________________________                                    

The polymerization reaction was continued at 50° C. for 3 hours, andthen the temperature of the reaction mixture was raised from 50° C. to65° C., taking 1 hour.

When the temperature of the reaction mixture reached 65° C., a mixtureof the following components was further added dropwise to the reactionmixture through a dropping funnel:

    ______________________________________                                                        Parts by Weight                                               ______________________________________                                        Methacryloyloxy ethyl tri-                                                                      1                                                           methylammonium chloride                                                       Methyl methacrylate                                                                             9                                                           Methanol          25                                                          ______________________________________                                    

The polymerization reaction was further continued for 20 hours, wherebya milky white dispersion liquid was obtained.

The conversion of the monomers was measured in the same manner as inExample 1. The result was that the conversion was 99.5%.

An extremely small amount of the milky white dispersion liquid wasdiluted by a large amount of distilled water, centrifuged, and thendispersed once again distilled water to remove unreacted components andthe dispersing agent therefrom, whereby purified polymer particles wereobtained.

The thus obtained polymer particles were inspected by a scanningelectron microscope. Spherical polymer particles with a substantiallyuniform particle size, with a plurality of hemispherical protrusionsbeing formed with substantially equal intervals therebetween on thesurface of the polymer particles, were observed. No newly formed finepolymer particles were found.

EXAMPLE 4

A dispersion liquid of polymer particles with a conversion of 92.1%,without protrusions on the surface of the polymer particles, wasobtained in the same manner as in Example 2.

Part of the dispersion liquid was sampled, and the polymer particlestherein were inspected by a scanning electron microscope. It wasobserved that spherical polymer particles with a smooth surface, and auniform particle size were formed.

The temperature of the polymer dispersion liquid was lowered to 60° C.,and a mixture of the following components for the formation ofprotrusions on polymer particles was added dropwise to the reactionmixture through a micro-feeder pump over a period of 4 hours:

    ______________________________________                                                        Parts by Weight                                               ______________________________________                                        t-butyl acrylamide sulfonic                                                                      5                                                          acid                                                                          Styrene           20                                                          2-propanol        50                                                          ______________________________________                                    

When the dropwise addition of the above components was completed, thetemperature of the reaction mixture was gradually raised to 80° C. overa period of 2 hours, and a solution composed of the following componentswas added dropwise to the reaction mixture from a dropping funnel, withstirring, over a period of 15 minutes:

    ______________________________________                                                      Parts by Weight                                                 ______________________________________                                        4,4'-azobis(4-cyano-                                                                          0.75                                                          pentanoic acid)                                                               2-propanol      10                                                            Distilled water 5                                                             ______________________________________                                    

The polymerization reaction was further continued at 80° C. for 8 hours,whereby a milky white dispersion liquid was obtained.

The conversion of the monomers was measured in the same manner as inExample 1. The result was that the conversion was 99.2%.

An extremely small amount of the milky white dispersion liquid wasdiluted by a large amount of distilled water, centrifuged, and thendispersed once again distilled water to remove unreacted components andthe dispersing agent therefrom, whereby purified polymer particles wereobtained.

The thus obtained polymer particles were inspected by a scanningelectron microscope. Spherical polymer particles with a substantiallyuniform particle size, with a plurality of hemispherical protrusionsbeing formed with substantially equal intervals therebetween on thesurface of the polymer particles, were observed. No newly formed finepolymer particles were found.

EXAMPLE 5

20 parts by weight of methanol were added to 3 parts by weight of acommercially available dye "Oil Black 860" (made by Orient ChemicalIndustries, Ltd.) and dissolved therein with the application of heatthereto. The mixture was cooled and filtered through a 1 μm microfilterto prepare a dye solution.

40 parts by weight of the milky white dispersion of the polymerparticles with a conversion of 98.7% which was finally obtained inExample 1 were added to 10 parts by weight of the above prepared dyesolution. The mixture was stirred at 50° C. for 2 hours and was thencooled to room temperature.

The cooled mixture was centrifuged and the supernatant was removedtherefrom, whereby a slurry of dyed polymer particles was obtained. Thethus obtained slurry of dyed polymer particles was dispersed again in amixed solvent composed of 50 parts by weight of methanol and 50 parts byweight of water, whereby a dispersion liquid was obtained.

The thus obtained dispersion was again centrifuged to obtain a slurry ofdyed polymer particles and the slurry was dispersed again in the samemixed solvent as mentioned above. This process was repeated once again,so that the same centrifuge and redispersing process was repeated threetimes in total, whereby a dispersion liquid of polymer particles dyedwith "Oil Black 860" was obtained.

The thus obtained dispersion liquid was dried by a commerciallyavailable small spray dryer (Trademark "Yamato Minispray" made by YamatoKagaku Co., Ltd.), whereby colored polymer particles were obtained.

0.5 parts by weight of a commercially available hydrophobic silica(Trademark "R972", made by Nippon Aerosil Co., Ltd.) were mixed with 100parts by weight of the above obtained colored polymer particles in amixer, whereby a toner No. 1 of the present invention for use inelectrophotography was obtained.

EXAMPLE 6

The procedure for preparing the toner No. 1 of the present invention inExample 5 was repeated except that the milky white dispersion of thepolymer particles with a conversion of 98.7% employed in Example 5 wasreplaced by the milky white dispersion of the polymer particles with aconversion of 99.3% which was finally obtained in Example 2, whereby atoner No. 2 of the present invention for use in electrophotography wasobtained.

EXAMPLE 7

The procedure for preparing the toner No. 1 of the present invention inExample 5 was repeated except that the milky white dispersion of thepolymer particles with a conversion of 98.7% employed in Example 5 wasreplaced by the milky white dispersion of the polymer particles with aconversion of 99.5% which was finally obtained in Example 3, whereby atoner No. 3 of the present invention for use in electrophotography wasobtained.

FIG. 1 shows a microscopic photograph of the above toner No. 3 taken bya scanning electron microscope. In the microscopic photograph,protrusions 2 are observed on the surface of the polymer particles 1.

EXAMPLE 8

The procedure for preparing the toner No. 1 of the present invention inExample 5 was repeated except that the milky white dispersion of thepolymer particles with a conversion of 98.7% employed in Example 5 wasreplaced by the milky white dispersion of the polymer particles with aconversion of 99.2% which was finally obtained in Example 4, whereby atoner No. 4 of the present invention for use in electrophotography wasobtained.

EXAMPLE 9

0.5 parts by weight of a surfactant of the following formula were addedto 100 parts by weight of the solid component contained in thedispersion liquid of polymer particles dyed with "Oil Black 860" whichwas finally obtained in Example 6 before the preparation of the tonerNo. 2 of the present invention, whereby a dispersion liquid wasprepared: ##STR9## The thus prepared dispersion liquid was stirred atroom temperature.

A small portion of the above dispersion liquid was placed in a vesseland gradually heated, with stirring, on a water bath, whereby themaximum temperature at which the colored polymer particles were notmerged into one lump or did not aggregate was determined to be 45° C.

Therefore, the remaining dispersion liquid was heated to 45° C. and wasstirred at 45° C. for 2 hours, then cooled, and filtered, whereby a cakeof colored polymer particles treated with the above-mentioned surfactantwas obtained.

The thus obtained cake of the colored polymer particles was dispersed ina mixed solvent composed of water and methanol (1:1 in volume ratio),and was then filtered, whereby a cake of the colored polymer particleswas obtained.

The thus obtained cake of the colored polymer particles was dried atroom temperature overnight and was then dried at 30° C. under reducedpressure until the weight of the cake became constant.

The thus dried, loosely coagulated cake of the colored polymer particleswas crushed in a mixer, whereby colored polymer particles treated withthe above-mentioned surfactant were obtained.

0.5 parts by weight of a commercially available hydrophobic silica(Trademark "R972", made by Nippon Aerosil Co., Ltd.) were uniformlymixed with 100 parts by weight of the above obtained colored polymerparticles in a mixer, whereby a toner No. 5 of the present invention foruse in electrophotography was obtained.

EXAMPLE 10

The procedure for the preparation of the toner No. 5 of the presentinvention was repeated except that the dispersion liquid of polymerparticles dyed with "Oil Black 860" employed in Example 9 was replacedby the dispersion liquid of polymer particles dyed with "Oil Black 860"prepared in Example 8 before the preparation of the toner No. 4 of thepresent invention, whereby a toner No. 6 of the present invention foruse in electrophotography was obtained.

COMPARATIVE EXAMPLE 1

The following components were placed in the same glass reaction vesselas employed in Example 1:

    ______________________________________                                                        Parts by Weight                                               ______________________________________                                        Methanol          60                                                          Ethanol           20                                                          Distilled water   10                                                          Polyvinyl pyrrolidone                                                                            2                                                          (weight average molecular                                                     weight: 40,000)                                                               ______________________________________                                    

The above mixture was stirred at room temperature and the polyvinylpyrrolidone was completely dissolved in the mixture.

The reaction vessel was placed in the same constant-temperature waterbath as employed in Example 1.

Nitrogen was introduced into the reaction vessel through thenitrogen-introducing tube, with the reaction mixture being cooled to 5°C. The concentration of oxygen in the gas phase in the reaction systemwas reduced to 0.1 vol. % or less by the replacement of oxygen with thenitrogen by being monitored with a Galvanic-battery type oxygenanalyzer.

When the temperature of the reaction mixture was cooled to 5° C., thefollowing components were added to the reaction mixture through thedropping funnel:

    ______________________________________                                                          Parts by Weight                                             ______________________________________                                        Styrene             20                                                        Methyl acrylate     10                                                        Ethyl acrylate      10                                                        n-dodecylmercaptane 0.15                                                      Divinyl benzene (converted to                                                                     0.5                                                       the amount of the effective                                                   component as being 100%)                                                      ______________________________________                                    

The concentration of oxygen in the reaction system increased to 0.5 vol.%. The oxygen was replaced with nitrogen, so that the concentration ofoxygen in the reaction system was reduced to 0.1 vol. % or less.

The temperature of the constant-temperature water bath was elevated to65° C., and when the temperature of the reaction mixture reached 60° C.,the stirring speed was set at 100 rpm, and a solution of an initiatorconsisting of the following components was added dropwise by a syringethrough the syringe inlet:

    ______________________________________                                                        Parts by Weight                                               ______________________________________                                        2,2'-azobis(2,4-dimethyl-                                                                       0.0016                                                      valeronitrile)                                                                Methanol          0.02                                                        ______________________________________                                    

The reaction mixture was transparent for about 15 minutes after theaddition of the solution of the initiator, but in about 15 minutes, thereaction mixture became milky white. The reaction mixture was thenallowed to stand for 30 minutes and became further milky white.

A solution composed of the following components was added dropwise tothe above milky white mixture through the dropping funnel over a periodof 15 minutes:

    ______________________________________                                                        Parts by Weight                                               ______________________________________                                        2,2'-azobis(2,4-dimethyl-                                                                       0.8                                                         valeronitrile)                                                                Methanol          10                                                          ______________________________________                                    

The polymerization was further continued for 5 hours and 30 minutes, anda mixture of the following components was added to the reaction mixturethrough a syringe:

    ______________________________________                                                         Parts by Weight                                              ______________________________________                                        α-thioglycerol                                                                             0.4                                                        1,3-dutanediol methacrylate                                                                      0.6                                                        Methanol           5                                                          ______________________________________                                    

The polymerization was further continued for 20 hours. Part of thereaction mixture was then sampled by a syringe and the conversion of themonomers was measured in the same manner as in Example 1. The result wasthat the conversion was 89.5%

Part of the dispersion liquid was sampled, and the polymer particlestherein were inspected by a scanning electron microscope. It wasobserved that spheric polymer particles with a smooth surface, and auniform particle size were formed.

The polymer particles in the above prepared dispersion liquid were dyedin the same manner as in Example 5, and a comparative toner No. 1 foruse in electrophotography was produced in the same manner as in Example5.

COMPARATIVE EXAMPLE 2

The following components were placed in the same glass reaction vesselas employed in Example 1:

    ______________________________________                                                        Parts by Weight                                               ______________________________________                                        Methanol          60                                                          Ethanol           20                                                          Distilled water   10                                                          Polyvinyl pyrrolidone                                                                            2                                                          (weight average molecular                                                     weight: 40,000)                                                               ______________________________________                                    

The above mixture was stirred at room temperature and the polyvinylpyrrolidone was completely dissolved in the mixture. The reaction vesselwas placed in the same constant-temperature water bath as employed inExample 1.

Nitrogen was introduced into the reaction vessel through thenitrogen-introducing tube, with the reaction mixture being cooled to 5°C. The concentration of oxygen in the gas phase in the reaction systemwas reduced to 0.1 vol. % or less by the replacement of oxygen with thenitrogen by being monitored with a Galvanic-battery type oxygenanalyzer.

When the temperature of the reaction mixture was cooled to 5° C., thefollowing components were added to the reaction mixture through thedropping funnel:

    ______________________________________                                                          Parts by Weight                                             ______________________________________                                        Styrene             20                                                        Methyl acrylate     10                                                        Ethyl acrylate      10                                                        n-dodecylmercaptane 0.15                                                      Divinyl benzene (converted to                                                                     0.5                                                       the amount of the effective                                                   component as being 100%)                                                      ______________________________________                                    

The concentration of oxygen in the reaction system increased to 0.5 vol.%. The oxygen was replaced with nitrogen, so that the concentration ofoxygen in the reaction system was reduced to 0.1 vol. % or less.

The temperature of the constant-temperature water bath was elevated to65° C., and when the temperature of the reaction mixture reached 60° C.,the stirring speed was set at 100 rpm, and a solution of an initiatorconsisting of the following components was added dropwise by a syringethrough the syringe inlet:

    ______________________________________                                                        Parts by Weight                                               ______________________________________                                        2,2'-azobis(2,4-dimethyl-                                                                       0.0016                                                      valeronitrile)                                                                Methanol          0.02                                                        ______________________________________                                    

The reaction mixture was transparent for about 15 minutes after theaddition of the solution of the initiator, but in about 15 minutes, thereaction mixture became milky white. The reaction mixture was thenallowed to stand for 30 minutes and became further milky white.

A solution composed of the following components was added dropwise tothe above milky white mixture through the dropping funnel over a periodof 15 minutes:

    ______________________________________                                                        Parts by Weight                                               ______________________________________                                        2,2'-azobis(2,4-dimethyl-                                                                       0.8                                                         valeronitrile)                                                                Methanol          10                                                          ______________________________________                                    

The polymerization was further continued for 5 hours and 30 minutes, anda mixture of the following components was added to the reaction mixturethrough a syringe:

    ______________________________________                                                         Parts by Weight                                              ______________________________________                                        α-thioglycerol                                                                             0.4                                                        1,3-dutanediol methacrylate                                                                      0.6                                                        Methanol           5                                                          ______________________________________                                    

The polymerization was further continued for 10 hours. Part of thereaction mixture was then sampled by a syringe and the conversion of themonomers was measured in the same manner as in Example 1.

The result was that the conversion of the monomers was 78.3%.

The temperature of the reaction mixture was lowered to 20° C. bydecreasing the set temperature of the constant-temperature water bath,and a mixture of the following components for the formation ofprotrusions on polymer particles was added dropwise from the droppingfunnel over a period of 2 hours:

    ______________________________________                                                         Parts by Weight                                              ______________________________________                                        Methacrylamide propyl tri-                                                                        1                                                         methylammonium chloride                                                       Methanol           40                                                         Distilled water    10                                                         ______________________________________                                    

When the dropwise addition of the above components was completed, thereaction mixture was stirred at a stirring speed of 70 rpm for 1 hour,with the temperature thereof raised to 50° C.

A mixture of the following components was then added dropwise from adropping funnel to the reaction mixture over a period of 30 minutes:

    ______________________________________                                                        Parts by Weight                                               ______________________________________                                        2,2'-azobisisobutyronitrile                                                                     0.4                                                         Methanol          7                                                           ______________________________________                                    

The polymerization reaction was continued at 50° C. for 3 hours, andthen the temperature of the reaction mixture was raised to 65° C.,taking 1 hour. The polymerization reaction was further continued for 20hours, whereby a milky white dispersion liquid was obtained.

Part of the milky white dispersion liquid was then sampled and theconversion of the monomers was measured in the same manner as inExample 1. The result was that the conversion of the monomers was 85.4%.

An extremely small amount of the milky white dispersion liquid wasdiluted by a large amount of distilled water, centrifuged, and thendispersed once again distilled water to remove unreacted components andthe dispersing agent therefrom, whereby purified polymer particles wereobtained.

Part of the dispersion liquid was sampled, and the polymer particlestherein were inspected by a scanning electron microscope. It wasobserved that spherical polymer particles with a smooth surface, and auniform particle size were formed.

The polymer particles in the above prepared dispersion liquid were dyedin the same manner as in Example 5, and a comparative toner No. 2 foruse in electrophotography was produced in the same manner as in Example5.

COMPARATIVE EXAMPLE 3

The colored polymer particles before being mixed with the hydrophobicsilica, obtained in Comparative Example 1, were treated so as to makethe surface thereof uneven as follows:

1880 parts by weight of ion-exchange water were placed in a reactionvessel including a separable glass flask equipped with a condenser, anitrogen-introducing tube, a stirrer with semicircular teflon blades, amotor for the stirrer, and a dropping funnel.

The temperature of the ion-exchange water was raised to 75° C., and theoxygen in the flask was replaced with nitrogen to a concentration of 0.5% or less.

20 parts of methyl methacrylate were added to the ion-exchange water inone lot through the dropping funnel, with stirring at a stirring speedof 200 rpm. The mixture was stirred, with the temperature thereofmaintained at 75° C., for 2 hours.

A mixture of the following components was added dropwise to the reactionmixture over a period of 1 hour:

    ______________________________________                                                        Parts by Weight                                               ______________________________________                                        Ion-exchange water                                                                              120                                                         Potassium persulfate                                                                            1.08                                                        Sodium styrenesulfonate                                                                         0.0384                                                      ______________________________________                                    

The above mixture was stirred for 3 hours, and a light milky whitedispersion liquid was obtained.

A mixture of the following components was added dropwise to the abovedispersion liquid over a period of 15 minutes:

    ______________________________________                                                      Parts by Weight                                                 ______________________________________                                        Ion-exchange water                                                                            87                                                            Potassium persulfate                                                                          2.08                                                          ______________________________________                                    

A mixture of the following components was further added dropwise to theabove mixture over a period of 4 hours:

    ______________________________________                                                       Parts by Weight                                                ______________________________________                                        Styrene          80                                                           n-butyl methacrylate                                                                           60                                                           Methyl methacrylate                                                                            60                                                           ______________________________________                                    

The above mixture was stirred at 75° C. for 10 hours, and was thencooled to room temperature. The thus obtained dispersing liquid wasfiltered through a 400-mesh filter to remove large polymer particlestherefrom, whereby a dispersion liquid of finely-divided polymerparticles was obtained. The thus formed finely-divided polymer particleswere inspected by a scanning electron microscope. The polymer particleswere spherical particles with a uniform particle size of 0.31 μm.

The thus obtained dispersion liquid of the finely-divided polymerparticles was placed in a round-bottom flask and was frozen so as toform a thin layer on the inside of the flask while the flask wasimmersed in an acetone solution cooled with dry ice and rotatedslantingly.

The flask was then incorporated into a freezing dryer and the content ofthe flask was dried for 10 hours, whereby finely-divided polymerparticles were obtained.

100 parts by weight of the colored polymer particles obtained inComparative Example 1 before being mixed with the hydrophobic silica,and 10 parts by weight of the above obtained finely-divided polymerparticles were mixed in a commercially available mixer (Trademark "OMDIZZER", made by Nara Machinery Co., Ltd.) at a speed of revolution of1000 rpm for 2 minutes, whereby the finely-divided polymer particleswere deposited on the surface of the colored polymer particles.

The thus prepared finely-divided-polymer-particles deposited coloredpolymer particles were inspected by a scanning electron microscope. Itwas observed that all the colored polymer particles bore thefinely-divided polymer particles, but the finely-divided polymerparticles were coagulated from place to place to a large extent.

The above mixture was then subjected to a fixing treatment by"Hybridization System NHS-1" (made by Nara Machinery Co., Ltd.) at 6000rpm for 3 minutes, whereby the finely-divided polymer particles werefixed to the surface of the colored polymer particles.

The above colored polymer particles were inspected by a scanningelectron microscope. It was observed that the coagulated finely-dividedpolymer particles disappeared. Undulations of 0.1 to 0.3 μm wereobserved on the surface of the colored polymer particles, but there wereno spherical finely-divided polymer particles on the surface of thecolored polymer particles, and the so-called protrusions in the presentinvention were not recognized on the surface of the colored polymerparticles.

COMPARATIVE EXAMPLE 4

100 parts by weight of the colored polymer particles obtained inComparative Example 1 before being mixed with the hydrophobic silicawere dispersed with stirring, with the application of ultrasonic wavethereto, in 100 parts by weight of ion-exchange water in which 0.33parts by weight of lauryl methyl ammonium chloride were dissolved,whereby a dispersion liquid was obtained.

To the thus obtained dispersion liquid were gradually added 100 parts byweight of the dispersion liquid of finely-divided polymer particlesobtained in Comparative Example 3 which was not yet subjected to thefreezing drying.

When 20 parts by weight of the dispersion liquid of finely-dividedpolymer particles were added to the first obtained dispersion liquid,the viscosity of the mixture was abruptly increased so high that it wasdifficult to stir the mixture. Therefore, with the number of revolutionfor the stirring increased, the remaining dispersion liquid offinely-divided polymer particles was added and mixed with the firstdispersion liquid, whereby a dispersion liquid was obtained.

The thus obtained dispersion liquid was inspected by an opticalmicroscope. It was observed that the finely-divided polymer particleswere not much coagulated, but the colored polymer particles were joinedvia the finely-divided polymer particles which served as the bridgestherefor.

Part of the above dispersion liquid was sampled and gradually heated. Asa result, when the dispersion was heated to 68° C., the dispersionliquid was completely coagulated and solidified. It was impossible tocrush the solidified dispersion even after dried because the coloredpolymer particles were fused and merged tightly.

For the above reason, the remaining above dispersion was subjected toheat treatment at 60° C. for 2 hours, filtered, washed and dried,whereby composite polymer particles were obtained.

0.5 parts by weight of a commercially available hydrophobic silica(Trademark "R972", made by Nippon Aerosil Co., Ltd.) were mixed with 100parts by weight of the above obtained composite polymer particles in amixer in the same manner as in Example 5, whereby a comparative tonerNo. 4 of for use in electrophotography was obtained.

The thus prepared comparative toner No. 4 was inspected by a scanningelectron microscope. As a result, it was observed that thefinely-divided polymer particles on the surface of the colored polymerparticles were not fused, but were deposited or attached thereto, withtheir spherical shapes retained. However, when the comparative toner wasplaced on a glass plate and some pressure was applied thereto by asilicone rubber blade, a large amount of the finely-divided polymerparticles were easily detached from the colored polymer particles.

The shape, charging characteristics, and operational performances ofeach of the toners produced above, when used in practice, in a copyingmachine, are shown in the following Table 2. The results shown in Table2 indicate that the protrusions formed on the surface of polymerparticles have significant favorable effects on the image transferperformance and cleaning performance, and the treatment of the polymerparticles with a surfactant has favorable effects on the environmentalstability. In contrast, finely-divided polymer particles merelydeposited on the surface of the polymer particles do not have anyconspicuous advantageous effects on any of the above-mentionedcharacteristics and performances of the toner.

                                      TABLE 2                                     __________________________________________________________________________                                              Ratio of                                                                      Charges in                                                                    charge                                                                        Quantity                                                      Ratio of        of Toner                                                      Protru-         by changes Clean-                                             sions-          in Envi-                                                                            Image                                                                              ing                                                occupying       ronmental                                                                           Transfer                                                                           Perfor-                  No     dv.sup.1)                                                                        dn.sup.1)                                                                        dv/dn                                                                             h.sup.2)                                                                         D.sup.2)                                                                         h/D                                                                              Area  q/m(1).sup.4)                                                                      q/m(2).sup.5)                                                                      Conditions                                                                          Ratio                                                                              mance                    __________________________________________________________________________    Ex. 5  5.26                                                                             5.18                                                                             1.015                                                                             0.3                                                                              5.1                                                                              0.06                                                                             8     +32  +16  65    92   4                        Ex. 6  6.12                                                                             6.01                                                                             1.018                                                                             0.4                                                                              6.0                                                                              0.07                                                                             15    -36  -19  60    93   4                        Ex. 7  5.43                                                                             5.32                                                                             1.021                                                                             1.1                                                                              5.3                                                                              0.21                                                                             9     +55  +32  52    99   5                        Ex. 8  6.48                                                                             6.32                                                                             1.025                                                                             1.3                                                                              6.3                                                                              0.21                                                                             17    -42  -22  61    99   5                        Ex. 9  6.18                                                                             6.06                                                                             1.019                                                                             0.4                                                                              6.1                                                                              0.07                                                                             15    -41  -30  32    92   4                        Ex. 10 6.51                                                                             6.36                                                                             1.024                                                                             1.3                                                                              6.4                                                                              0.20                                                                             17    -48  -46   5    99   5                        Comp. Ex. 1                                                                          5.16                                                                             5.08                                                                             1.016                                                                             0  5.1                                                                              0  0     +25   +6  120   65   1                        Comp. Ex. 2                                                                          5.17                                                                             5.07                                                                             1.019                                                                             0  5.1                                                                              0  0     +35  +16  73    53   1                        Comp. Ex. 3                                                                          5.43                                                                             5.08                                                                             1.068                                                                             --.sup.9)                                                                        5.2                                                                              --.sup.9)                                                                        --9)  -21   -8  90    74   2                        Comp. Ex. 4                                                                          7.23                                                                             5.48                                                                             1.32                                                                              0.2                                                                              6.0                                                                              0.03                                                                             5     -27   -7  115   81   .sup.  2.sup.10)         __________________________________________________________________________

In the above table, notes 1) to 10) denote as follows:

1) dv and dn respectively represent the volume mean particle size ofparticles and the number mean particle size with a unit of μm, which areobtained by Coulter counter by counting 30,000 particles, using a 100 μmaperture tube.

2) h and D respectively represent the average height of the protrusionsmeasured from the surface of the polymer particles to the top thereof,and the average diameter of the polymer particles without including theprotrusions. These average values are obtained by measuring the externalshapes of 10 toner particles chosen arbitrarily by a scanning electronmicroscope.

3) The ratio of protrusions-occupying area is the ratio of the area onthe surface of the polymer particles occupied by the protrusions to theentire surface of the polymer particles. These areas are measured fromthe external shapes of the particles by a scanning electron microscope.

4) q/m(1) represents the quantity of electric charge per unit weight ofa toner, with a unit of μC/g, measured at 10° C., 15% RH (relativehumidity). The quantity of electric charge is measured by the steps of(1) mixing 2 parts by weight of the toner with 100 parts by weight of acarrier comprising silicone-coated iron carrier particles at 10° C., 15%RH (relative humidity), (2) charging the toner by vigorously stirringthe toner under the application of high electric field thereto, and (3)separating the toner from the carrier by blowing the mixture of thetoner and the carrier.

5) q/m(2) represents the quantity of electric charge per unit weight ofa toner, with a unit of μC/g, measured at 30° C., 90% RH (relativehumidity), with the same steps as in the case of q/m(1).

6) The ratio of charges in charge quantity of toner by the changes inthe environmental conditions is indicated by{[q/m(1)-q/m(2)]/1/2[q/m(1)+q/m(2)]}×100%. The larger the value of thisratio, the larger the variation in the charge quantity of the tonerdepending upon the changes in the environmental conditions.

7) In the case of a toner which is negatively charged, the imagetransfer ratio thereof is determined by the steps of making toner imageson a photoconductor df a commercially available copying machine(Trademark "IMAGIO 420", made by Ricoh Co., Ltd.), stopping the copyingmachine during an image transfer step to take out the photoconductor,and sampling the quantity of the toner from the surface of thephotoconductor by use of an adhesive tape, that is, the amount of thetoner obtained from the surface of the photoconductor by the adhesivetape before the image transfer (after the development), and the amountof the toner obtained from the surface of the photoconductor by theadhesive tape after the image transfer, and determining the value of theimage transfer ratio in accordance with the following formula:

    [Amount of toner remaining on the photoconductor after image transfer]/[Amount of toner deposited on the photoconductor before image transfer (after development)]×100%.

In the case of a toner which is positively charged, the image transferratio thereof is determined in accordance with the same procedure asmentioned above except that the copying machine "IMAGIO 420" is replacedby a commercially available copying machine (Trademark "FT 4520", madeby Ricoh Company, Ltd.).

8) The cleaning performance is determined by any of the above-mentionedcopying machines by the steps of making 100 A-3 size copies of a solidblack image, stopping the copying machine in the course of a cleaningstep for a 101 the copy, taking out the photoconductor from the copyingmachine, and sampling the toner remaining on a cleaning blade for thephotoconductor by use of an adhesive tape. In the evaluation shown inTable 2, the larger the number, the better the cleaning performance.

9) "-" denotes that the shape of protrusions is not clear andprotrusions cannot be recognized.

10) A film of finely-divided polymer particles is formed on the surfaceof the photoconductor in its entirely.

What is claimed is:
 1. A polymerization method comprising the stepsof:polymerizing a vinyl monomer in the presence of a polymericdispersing agent in a hydrophilic organic liquid in which said vinylmonomer is soluble, but in which a polymer formed from said vinylmonomer swells or is substantially insoluble, optionally in the presenceof a cross-linking agent and a chain transfer agent, thereby preparingfirst polymer particles, said dispersing agent, said liquid, saidmonomer and said particles when prepared constituting a polymerizationsystem; and continuing the polymerization with the addition to saidpolymerization system of a vinyl monomer which, when polymerized,provides a polymer with a glass transition point higher than that ofsaid first polymer particles, and an anionic monomer or a cationicmonomer, thereby producing polymer particles which are substantiallyspherical and have protrusions on the surface of each polymer particle,with a narrow particle size distribution.